BAGHDAD, April 20: Twenty-two prisoners were killed and nearly 100 were injured on Tuesday when 12 mortar rounds slammed into a US-run detention facility west of Baghdad, military officials said.

Brig Gen Mark Kimmitt, the US-led authority's deputy director of military operations, said at a press conference the rounds hit the Baghdad Confinement Facility at Abu Ghraib, 20kms west of the Iraqi capital.

Ninety-two people were injured and 25 of the most badly hurt were taken away by helicopter, some to the fortified green zone in the centre of Baghdad for treatment. Brig Kimmitt said he did not know whether the victims were suspected criminals or "security detainees" from US-led operations in the country.

A military spokesman said later that 4,400 "security detainees" were held at the jail, one of the largest US-run prison facilities in Iraq. In February, guerillas fired 33 mortar bombs and five rockets at the prison before US troops shot one person dead and arrested 55. Barely a week earlier, another Iraqi civilian was hurt in an attack.

Last August three mortar rounds were fired into the complex, killing six Iraqi detainees and injuring many more. Early reports indicated that 18 rounds had been fired at the security facility, but the US military later downgraded it to 12. A military spokesman said nobody had been detained over the attack.

The International Committee of the Red Cross (ICRC) said according to figures it has been given by the Coalition Provisional Authority, the facility holds some 6,500 inmates, of which about 2,000 are inside for criminal offences. The Iraqi Red Crescent was called in to help because of the scale of the wounded at the prison.

The prison has remained a top-security institution since the Americans took it over from the old government, allowing Red Cross officials to visit, but denying journalists access to the site. According to CPA estimates last month, some 8,000 Iraqis were being held in the strife-riven country's jails because they are considered to be a threat to security.

However, hundreds were released last month since they were no longer deemed dangerous. Brig Kimmitt said about 250 detainees were being released every week. Human rights groups have complained that many detainees have been held in squalid conditions and that some of them had been mistreated.

'RAT'S NEST': The top US general said on Tuesday that Fallujah was "a rat's nest" that will have to be dealt with in part through the use of military force.