The UN observer mission to Sierra Leone blames the rebels for untold numbers of random killings, mutilations, and rapes and the destruction of a fifth of the capital's buildings.

But the UN document also acknowledged that there had been reports that the West African peacekeeping force Ecomog had been "summarily executing detainees who were allegedly either rebels or rebel sympathisers".

Jon Leyne reports: Much of the killing was entirely arbitrary

The report said that the actual number of civilian casualties suffered during last month's attack on Freetown would never be known, although one mortuary worker said on 25 January that over 2,000 bodies of men, women and children had already been disposed of.

A large number of bodies were believed to have been left in ruined buildings or to have been hastily buried on waste ground.

Since rebel forces had renewed their offensive against Sierra Leone's democratically elected government in December, conservative estimates put the total casualty figure at between 3,000 and 5,000, said the UN report.

Many rebel soldiers were children, the report said

It says the rape of women and girls appears to have been standard practice for the rebels.

Many of the soldiers on the rebel side were children, with some as young as eight.

Rebels advancing through Freetown on 6 and 7 January had "frequently forced civilians into the streets for use as human shields".

Much of the killing had seemed to have been completely arbitrary, the document said, and a number of those interviewed had described "the execution of the entire population of residential compounds" for refusing to obey instructions to dance and make music on the streets.

"Killing occasionally occurred in the context of games in which people were lined up and the executioners teasingly chose who to kill, and who to spare," the report said, adding that perpetrators were often said to have been under the influence of cocaine, other drugs or alcohol.

Food crisis warning

Peacekeepers: 'Made no effort' to establish guilt of victims

UN Secretary-General Kofi Annan presented the report to a closed meeting of the Security Council before its public release on Friday.

The contents of the report emerged as the UN World Food Programme warned that continued fighting in the capital threatens to put the city's entire population at risk of a large-scale food crisis in as little as three weeks.

Although human rights violations by the Nigerian-led Ecomog force and Sierra Leone's Civil Defence Forces did not match the scale of rebel atrocities, they were nonetheless totally unacceptable, the report said.

Interrogation 'inadequate'

Human rights monitors in Sierra Leone's UN observer mission had witnessed one execution by the peacekeeping force and said "witnesses of the highest probity" had reported that they were present at others.