Obama: Boston bombings being investigated as ‘act of terrorism’

WASHINGTON -- The FBI is investigating the double bombings at the Boston Marathon as an “act of terrorism,” President Obama said Tuesday as he vowed to find the perpetrators of what he called a “heinous and cowardly act.”

“Any time bombs are used to target innocent civilians, it is an act of terror,” Obama said.

Making his second public statement on the attack in less than 24 hours, Obama told reporters that investigators did not know yet whether the bombs were the work of an individual or an organization, or whether the attacker had foreign ties.

“Clearly we’re at the beginning of our investigation. It will take time to follow every lead and determine what happened. But we will find out. We will find whoever harmed our citizens, and we will bring them to justice,” Obama said. “We also know this: The American people refuse to be terrorized.”

FULL COVERAGE: Boston Marathon attack

Obama had not used the word “terrorism” when he spoke about the attack Monday, just hours after the two explosions turned the crowded race finish line into a chaotic and bloody scene. Three people were killed and more than 140 were injured, law enforcement officials say.

Although White House officials later characterized the attack as an “act of terror,” Obama’s remarks on Tuesday suggested a more formal, legal designation.

The wording also carries some emotional weight. The White House has sought to keep the president prominently engaged in the response to the attack. Obama and his team are mindful of his “ministerial” role in a crisis, former top advisor David Axelrod noted on MSNBC on Tuesday.

Speaking Tuesday, Obama praised the first responders who rushed to care for the wounded, churches which opened their doors to visitors and residents who donated blood after the attack.

“So if you want to know who we are, what America is, how we respond to evil, that’s it: selflessly, compassionately, not afraid,” Obama said.

VIDEO: Boston marathon explosion

Obama has requested frequent briefings on the response and investigation in Boston, officials said. Tuesday morning, the president met with Homeland Security Secretary Janet Napolitano, Atty. Gen. Eric Holder, FBI Direct Robert Mueller and other security advisors.

But other daily business at the White House continues. As of mid-morning, the president’s daily schedule included a meeting with Sens. John McCain, (R-Ariz.) and Charles Schumer (D-N.Y.) on immigration reform, a working lunch with Crown Prince Mohammed Bin Zayed of the United Arab Emirates and an East Room ceremony honoring NASCAR Sprint Cup Series champion Brad Keselowski.

Still, there were signs of the tragedy at the White House. Pennsylvania Avenue in front of the White House remained blocked to pedestrians with yellow police tape, and Secret Service agents kept tourists and onlookers at a distance in Layafette Park.

The flag flying over the White House was lowered to half staff “as a mark of respect for the victims of the senseless acts of violence perpetrated on April 15, 2013, in Boston,” according to a proclamation Obama issued Tuesday ordering all military posts and public building do the same.

PHOTOS: Explosions at Boston Marathon

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Kathleen.Hennessey@latimes.com

Twitter: @khennessey

Christi.Parsons@latimes.com

Twitter: @cparsons