Muhammad is a former US soldier who served in the Gulf War

Judge James Ryan issued an order after doctors had said Muhammad was at risk of serious injury or death if he continued to refuse taking food.

Muhammad, 44, is currently awaiting a second murder trial in Maryland.

Last year, he was sentenced to death in Virginia for one of 10 sniper-style killings in several states in 2002.

Muhammad and his co-defendant Lee Boyd Malvo are accused of the shootings in a three-week killing spree in October.

Malvo, 20, was sentenced to life in jail for a separate killing in Virginia.

'Reasonable force'

Muhammad had refused to take food since he was transferred from a Virginia prison, said the director of the Department of Correction and Rehabilitation in Maryland's Montgomery County, Arthur Wallenstein.

The two men shot their victims from inside the boot of their car

Muhammad, a former US soldier, was reportedly upset with the food he was being served in Maryland and the handling of his legal material.

Mr Wallenstein said his agency had sought authority to be "allowed to hydrate and feed" Muhammad.

Judge Ryan's order said corrections officials "may administer necessary nourishment, hydration and medical care" by using - if necessary - "medically reasonable force".

Muhammad was convicted of the killing of Dean Meyers on 9 October 2002 in Manassas and of murdering "at least one other person".

Malvo was sentenced for a shooting in Falls Church.

Montgomery County prosecutors had pressed for the two men to be tried in Maryland as insurance, in case these Virginia convictions are overturned.

The shootings were carried out from the back of a specially converted car.