In the wake of what President Obama described as an “act of terror” at the Boston Marathon, security remained tight in Boston and other major cities worldwide Tuesday. Retailers near where the two bombings struck reopened, although customer traffic remained sparse.

“While there is no current indication to suggest that the events in Boston are indicative of a broader plot, out of an abundance of caution, DHS [Department of Homeland Security] continues to keep in place enhanced security measures at transportation hubs, utilizing measures both seen and unseen,” secretary of Homeland Security Janet Napolitano said Tuesday. “We continue to urge the American public to remain vigilant and immediately report any signs of suspicious activity to local law enforcement officials.”

This story first appeared in the April 17, 2013 issue of WWD. Subscribe Today.

At a press conference Tuesday afternoon in Boston, Federal Bureau of Investigation and law enforcement authorities said the investigation is now a worldwide one. The President will travel to Boston Thursday to speak at an interfaith service dedicated to those who were gravely wounded or killed in the bombing in Boston. At press time, three people had been killed and 176 were injured, including 17 critically.

Area retailers tried to regain their footing. Among the stores that reopened were Saks Fifth Avenue, Jack Wills and Scoop. Ron Frasch, president and chief merchant of Saks Fifth Avenue, which operates a store at 800 Boylston Street, was uncertain what to expect for business in the days ahead. Frasch said, “Really, I have no idea. We have to wait and see, but folks in Boston are pretty resilient. This was a horrible occurrence, so this is not the most important thing to worry about.” Saks evacuated its store right after the bombings and was temporarily used as a staging area for the FBI.

Craig Johnson, president of Customer Growth Partners, said, “That’s a big shopping area — Newbury Street, Copley Place, Prudential Center [shopping mall]. There is a lot of retail in the immediate vicinity. That will have an impact for a while. There may be a reluctance for people to go in the area to shop for the short term, just this month. By the turn of the month, the local area should be back on track. Out of Boston area proper, people will continue spending.”

Johnson has analyzed the impact that natural disasters and terrorist events around the world have had on retailers over the past 20 years and has concluded that generally there is a “momentary” drop in business, then the same sales trends resume through the same month. “The only exception was 9/11 when sales actually declined nationally for a month. By Christmas, sales were back up again” on a national basis. “People are amazingly resilient. However, the New York metro area took several months to rebound, and tourism took a big hit for a good year,” Johnson noted. With the Boston bombings, “The impact will be more micro than macro. The Back Bay area will be challenged for a while but will come back strong,” Johnson said.

Alexia Ash, head of North America Forecasting for Exclusive Analysis Ltd. speculated that planting the explosive devices near the finish-line crowd indicated an intent was to cause mass casualties rather than targeting specific individuals or assets.

The Prudential Center reopened Tuesday, but 20 of the mall’s 75-plus stores and restaurants opted to remain shut. Shoppers were not allowed to access the complex from the Boylston Street entrances, only through the Huntington Avenue ones. A spokeswoman for its parent company, Boston Properties, declined to comment on the pace, but a few retailers described the local scene as subdued with “very light” foot traffic.

Oliver Mak, owner of the cutting-edge streetwear store Bodega, said many out-of-town runners dropped by Tuesday but they weren’t really shopping. “Everyone wants to be around other people just to feel normal. That’s what we’re doing — just talking about stuff — group therapy,” he said. “Retail is going to be pretty much a disaster for a while.”

Nearby at Copley Place, a 75-store upscale mall in the Back Bay neighborhood, Montblanc was the only store that kept its doors closed Tuesday, according to a spokesman on the premises. “Extremely quiet” was how he described the level of shopping. Neiman Marcus opened its location there at 11 a.m., after receiving the green light from local authorities. “Our associates were pleased to be back to a semblance of normal activity,” a Neiman Marcus spokeswoman said, noting how they rallied Monday, providing water, towels and assistance to runners and other people displaced by the lockdown.

Vineyard Vines’ staffers in the Prudential Center also rose to the occasion, after being in lockdown for hours in a stockroom with shoppers who were in the store when the bombs went off. Chief executive officer and cofounder Shep Murray said, “Yesterday was a scary day for everyone. We are incredibly proud of how our team handled the situation, keeping themselves and our customers safe and calm throughout. In the aftermath, our team provided clothing to those in need, found hotel rooms [for displaced runners] and even walked customers home so they would not be alone.”

NikeTown Boston at 200 Newbury Street remained shut Tuesday and a company spokeswoman could not say when it would reopen. Talbots’ store at 500 Boylston Street also stayed closed, as did Lululemon’s locations in the Prudential Center and on Newbury Street.

Boston-based Rue La La posted a message on its Web site Tuesday, expressing solidarity for the victims and saying it would not open at the normal time of 11 a.m. to observe a period of silence on the site. Rue opened for business at 3 p.m.

Marathon Sports, a seven-unit specialty retailer that has a store located next door to one of the explosions, encouraged visitors to its Web site to carry on. The company’s Twitter feed was posted on its homepage with the lead item being “Surreal morning. Know this: Boston is strong, and the running community is unified. We will persevere, prosper and we will run again.”

Security was stepped up in other major cities around the globe. With the Virgin London Marathon set for Sunday and Baroness Margaret Thatcher’s funeral today, British police and national security forces were stepping up safety measures. Having secured such high-profile events as the Royal Wedding in 2011 and the Queen’s four-day Diamond Jubilee and Summer Olympics last year, London’s police forces, MI5, and the British military will no doubt use that experience to their advantage in the next five days. With 36,000 registered runners, hundreds of thousands of spectators are expected to line the 26.2-mile marathon course that ends on The Mall.

St. James’ Palace said Tuesday that Prince Harry still planned to attend the marathon, where he will present medals to the winners at the finish line. “The London Marathon fully expects — at this stage — that the [event] will go ahead as planned on Sunday, although we are continuing to review security with the MP in the coming days,” said Nick Bitel, chief executive of the London Marathon.

According to the U.K. government services Web site, the terrorism threat level in mainland Britain from international terrorism remains “substantial,” meaning that an attack is a “strong possibility.”

A 30-second moment of silence will be held before the race, and runners have been encouraged to wear black ribbons, which will be handed out at the Expo with race numbers.

For Thatcher’s funeral procession, London’s Metropolitan Police said Tuesday that 4,000 officers from the Metropolitan Police Service, City of London Police and the British Transport Police will be on patrol. A spokesperson from the Metropolitan Police declined to comment on whether the number of police had been boosted in the wake of the Boston explosions.

More than 2,000 guests are expected to attend the funeral service at St. Paul’s Cathedral. Police, however, could not confirm the number of people expected to line the streets for the procession, which will take Thatcher’s coffin from Westminster Palace to St. Paul’s.

An expert with knowledge of the security operations at the London Games told WWD the highest-risk areas at both London events are likely to be the start and finish points. “There will be a plan in place to sweep for bombs with dogs ahead of the London events, and at this point, there’s not much more that they can do that they weren’t probably already doing,” the source said.

France, meanwhile, has also tightened security in public buildings and on public transport. On Monday, Interior Minister Manuel Valls ordered increased police patrols and called on members of the public to look out for suspicious packages, but he urged people not to panic. The government said so far it has no plans to upgrade its alert status from the current “strong red,” which it implemented in January after it launched military action in Mali.

With more than 10 million visitors coming to New York City on any given business day, Police Commissioner Ray Kelly bolstered police presence on the streets and the subway. One officer stationed outside the Mandarin-Oriental Hotel in the Time Warner Center said the force’s aim was first and foremost to make its presence known. “We want to be more visible to the people on the streets,” he said.