Foreign Office Minister Geoff Hoon said that with fresh evidence of the horrors of ethnic cleansing being uncovered "by the hour" the final death toll could be more than 10,000.

His warning came as war crimes inspectors moved in to examine a suspected torture and rape centre discovered by UK troops at a building that was the headquarters of the Serb military police in Pristina.

Nato has also revealed that there have been reports, some confirmed, of fresh atrocities being committed by withdrawing Serb forces.

MPs are debating the latest developments in the Kosovo crisis on Thursday afternoon.

'Final toll may be much worse'

Geoff Hoon: Stunned by what fellow human beings are capable of

Speaking at the daily Ministry of Defence briefing, Mr Hoon said: "Tragically, our estimates of the number of innocent men, women and children killed will almost certainly have to be revised upwards.

"According to the reports that we had gathered mostly from the refugees it appeared that around 10,000 people had been killed in more than 100 massacres. The final toll may be much worse," he said.

Geoff Hoon: Our estimates of the number of people killed will have to be revised upwards

"It is still hard to credit that our fellow human beings could be guilty of machine-gunning children, systematic rape of young women and girls, digging mass graves and burning bodies to try and conceal the evidence, but this has happened in Kosovo."

He went on to describe some of the grisly discoveries made inside the five-storey torture centre.

"The British forces have found knives, rubber and wooden batons, baseball bats with Serb slogans carved into them, a wooden crate full of knuckle-dusters, savage pornography and drugs, presumably used to sedate victims," he said.

British troops display some of the implements found in the torture centre

The minister added that the UK was determined that all evidence of atrocities should be gathered quickly.

More UK police officers and forensic scientists were being sent to Kosovo to assist in investigations that could lead to war crimes trials, he said.

Mr Cook told MPs: "I want those who ordered the murders, the brutality, the tortures to know that we will spare no effort to bring them to justice."

Refugees warned against revenge

Mr Hoon urged the returning refugees not to try to take the law into their own hands.

"We appeal to Kosovo Albanians to show restraint despite the appalling discoveries that they are making as they return to the ghost towns and burned-out villages without the loved ones who were killed by the Serb forces.

"We appeal to them not to go home to seek revenge. We want decent, ordinary peace-loving Serb families to stay so that Kosovo can be come a demonstration to the rest of Serbia of a modern multi-cultural society."

'Atrocities continue'

However, the UK chief of joint operations said that while the Kosovo Liberation Army appeared to behaving "responsibly", Serb forces were carrying out further violence as they withdrew.

UK armed forces say the Kosovo Liberation Army has generally acted responsibly

Admiral Sir Ian Garnett told the MoD briefing: "While the timetable of Serb withdrawal is being met, the nature of those withdrawals has sadly been characterised by the sort of behaviour that caused the alliance to act in the first place.

"There have been several reports of atrocities being committed as the Serbs withdraw, not all of which we have been able to confirm.

"Retreating Serbs have been burning houses, some people have been shot, and our forces remain alert to the possibility of booby traps.

"The picture overall is of Serbs trying to make it as difficult as possible for Kosovars to return safely to their homes."

By contrast, he said, some KLA fighters had disarmed and there were reports that some had begun clearing landmines.