Police Officer Shot Dead At Massachusetts University, near Boston

Police hunt the killer of a police officer shot dead at a university campus near Boston, days after the twin marathon bombings.

Gunfire and explosions have reportedly been heard in the hunt for the killer of a police officer shot dead at a Massachusetts university, near Boston.

The officer was responding to a report of a disturbance on Thursday night when he was shot multiple times.

A message on the Massachusetts Institute Of Technology (MIT) website described the incident as "active and extremely dangerous".

University students have been warned to stay indoors

It said police were sweeping the campus in Cambridge and urged people to remain indoors until further notice - and to stay away from the Stata Building, in particular.

Cambridge Police Department said in a statement that six gunshots were heard at 10.50pm local time.

Officers are currently sweeping the campus and searching for the suspect.

The officer, who was not immediately identified, was taken to a hospital and was pronounced dead from his wounds.

The university warned students in an emergency alert to stay indoors and said that one building on campus had been surrounded by police.

About 11,000 people attend the prestigious school.

Sky's US correspondent Dominic Waghorn in Boston, said: "We have a number of incidents - some of them ongoing - and what's not clear is whether they are linked.

"We do know that gunfire and explosions are reported in streets close to the Massachusetts Institute Of Technology after a police officer was shot dead there.

"People there, reporters there and eyewitnesses have said one person there has been shot in the gun battle that went on there.

"The pictures we are seeing on local television are of what we think is a gunman lying on the ground. Now it is not clear whether he is dead or whether he is being held there and forced to lie immobile.

"What is also going on in a similar area. but not exactly in the MIT area, is a huge police operation including FBI units and Homeland Security units - interesting because they wouldn't normally be called in for the shooting of a policeman.

"They would be called in if there was some kind of terrorist activity or some other event that would draw in federal agents."

It comes just days after two bombs exploded near the finish line of the Boston marathon, killing three people and injuring more than 180 others.

The FBI have released pictures and video of two suspects in the deadly Boston marathon bombings.