Senate Intelligence Committee Chairman Dianne Feinstein (D-Calif.) said she believes the attacks Monday afternoon in Boston constitute a terrorist attack.

"I think it was an attack, we don't know whether it was homegrown...or a foreign perpetrator," she told reporters.

Feinstein said she based her assessment on early news reports and comments made by local government officials.

Sen. Susan Collins (R-Maine) said her staff has been told by the National Counterterrorism Center that there was no specific warning of the Boston attacks.

Based on her own early assessment of the incident, "I believe this attack bears all the hallmarks of a terrorist attack," Collins said.

Collins is well-versed on intelligence and counterterrorism matters as a member of the Senate intelligence Committee and the former ranking Republican on the Senate Homeland Security and Governmental Affairs Committee.

She said she hadn't been briefed on specifics and said at least some senators expect to receive an intelligence briefing later tonight from senior federal officials.

Sen. Saxby Chambliss (R-Ga.), ranking member on the Senate Intelligence Committee, said Monday afternoon that intelligence officials appear to have had no advance warning of any specific attack in Boston.

“We had no advance warning and it’s just frustrating,” he told reporters. “But that’s the reason we need to make sure they've got all the tools that we need to try to figure out some way to interrupt and disrupt and pick up from these types of things.”