Obama spoke on the bombings at a Tuesday press conference, calling the incident "heinous and cowardly."
"This was a heinous and cowardly act. And given what we now know about what took place, the FBI is investigating it as an act of terrorism," Obama said. "Any time bombs are used to target innocent civilians it is an act of terror. What we don’t yet know, however, is who carried out this attack, or why; whether it was planned and executed by a terrorist organization, foreign or domestic, or was the act of a malevolent individual. That's what we don't yet know. And clearly, we’re at the beginning of our investigation."
The AP reports:
WASHINGTON — President Barack Obama will visit Boston on Thursday, three days after a pair of deadly bombings at the Boston Marathon.
Massachusetts Gov. Deval Patrick says Obama will be attending an interfaith service.
Three people were killed at the marathon's finish line, including an 8-year-old boy. More than 170 were wounded.
Hours after the explosions, Obama vowed that those responsible would be brought to justice. In remarks on Tuesday, he called the bombings an act of terrorism but said investigators still don't know who carried them out.
He also said the American people refuse to be terrorized.
Obama has traveled four times to cities reeling from mass violence, but all of the previous trips followed shooting incidents. The most recent was in December after the schoolhouse shooting in Newtown, Conn.
This story is developing.