Boston, Apr 19 (IANS): A suspect in the Boston Marathon bombings was captured but later died Friday, while a second one is on the loose, police said.

"One suspect dead. One at large," Boston Police Commissioner Ed Davis wrote on his official Twitter account.

He said the surviving fugitive is armed and dangerous, Xinhua reported.

The first suspect was caught naked in Watertown near Boston after a police officer was shot dead on the campus of the elite Massachusetts Institute of Technology (MIT).

The suspect was later confirmed dead. It was not clear how the suspect died.

A massive manhunt was earlier launched by the Federal Bureau of Investigation (FBI) and hundreds of state and local policemen.

Police informed inhabitants of the neighbourhood not to open their doors since the second individual was still in Watertown.

Police said they would conduct a door-to-door search.

"We believe this to be a terrorist. We believe this to be a man who has come here to kill people," Police Commissioner Davis said.

Police also said they would conduct a controlled detonation there.

Gunfire and blasts were reported in streets near the MIT as police reportedly chased the second suspect.

Three people were killed and over 170 others injured in the Boston Marathon bombings.