Dzhokhar Tsarnaev
Dzhokhar Tsarnaev, 19, is searched by law enforcement officers upon arrest in Watertown (Reuters)

Boston Marathon bombing suspect Dzhokhar Tsarnaev has been released from a civilian hospital and moved to prison.

Tsarnaev, 19, was hospitalised at Beth Israel Deaconess Medical Center, Massachusetts, for injuries he suffered in a shootout with police at the end of a massive manhunt last week.

Drew Wade, a spokesman for the US Marshals Service, said that the suspect "is now confined at the Bureau of Prisons facility FMC Devens at Ft. Devens, Massachusetts" which is located about 40 miles (65km) west of Boston.

The FBI said his condition improved from "serious" to "fair" earlier this week.

The prison lies in the decommissioned Fort Devens US Army base, and is dedicated to the treatment of detainees requiring specialised long-term medical or mental health care.

Tsarnaev is recovering from a bullet wound in his throat - which prevented him from speaking - and other injuries he sustained in the shoot-out, which began after he was discovered in a boat beneath a tarpaulin in the suburb of Watertown.

His elder brother Tamerlan, 26, was killed in an earlier shootout with police, which took place in the immediate aftermath of the explosions.

Cooperating with the authorities

Despite his communication impairment, Dzhokhar Tsarnaev has been cooperating with authorities from his hospital bed.

He reportedly told investigators he and Tamerlan were planning to carry out another attack in New York City's Time Square before they were caught.

 "We don't know that we would have been able to stop the terrorists had they arrived here from Boston," NYC Mayor Michael Bloomberg said. "We're just thankful that we didn't have to find out that answer."

Authorities believe the brothers carried out the deadly attack that killed three people and injured 264.

Dzhokhar Tsarnaev has been charged with conspiring to use weapons of mass destruction to kill and he could face the death penalty if convicted.