In a 56-page report, the human rights group said 20 percent of clients at Kosovo brothels staffed by trafficked women were members of the Serbian province's NATO peacekeeping force (KFOR) or UN administration (UNMIK).

"It is outrageous that the very same people who are there to protect women and girls are using their position and exploiting them instead, and they are getting away with it," Sian Jones, an Amnesty researcher told reporters on presenting the document.

The report noted: "Women and girls are sold into slavery.... They are threatened, beaten, raped and effectively imprisoned by their owners."

"With clients including international police and troops, the girls and women are often too afraid to escape and the authorities are failing to help them."

Many women were arrested themselves if they escaped, or were given no protection if they chose to testify in court, the London-based organisation said.

The report said women were trafficked into Kosovo predominantly from Bulgaria, Moldova, Romania and Ukraine, the majority of them via Serbia and often on promises of work in European Union member states.

At the same time, increasing numbers of local women and girls were being coerced into the sex trade, or trafficked out of Kosovo to EU countries including Britain, Italy and the Netherlands.

Amnesty gave chilling first-hand accounts from trafficked women and girls. It quoted one as saying: "'We were his property,' he said.

"By buying us, he had the right to beat us, rape us, starve us, and force us to have sex with clients."

Another rescued woman was quoted as saying: "Even when it was cold weather I had to wear thin dresses. I was forced by the boss to serve international soldiers and police officers."

But UNMIK said in a statement it considered the report outdated and "highly unbalanced".

"The report contains many generalizations, but misses these essential points: criminal gangs are exploiting vulnerable people, while law enforcement authorities in Kosovo are addressing the problem and making some progress," the UN said in a statement.

Amnesty said women were often sold several times in transit. It cited figures from the International Organization for Migration as saying some women were sold for as little as 50 euros (60 dollars).

The majority were forced to have unprotected sex. To date, not a single trafficked woman has obtained compensation for the abuses she endured, the report said.

Dick Oosting, director of Amnesty's EU office in Brussels, said the bloc was honour-bound to do more, both financially and legally, to help fight a "deplorable practice... which is occurring right on the doorsteps of the EU".

"More needs to be done at EU level to prevent trafficking, as well as protect the victims, whose rights are frequently left unprotected by the law," he said.

Amnesty said action was also needed from KFOR and UNMIK to prevent the trafficking in the first place and to ensure that women who escape their captors are safe from reprisals.

It also called on KFOR and UNMIK to ensure that its personnel, "if reasonably suspected of abuses of human rights and criminal offences in connection with trafficking... are brought to justice".

Kosovo has been under UN administration since June 1999, after NATO bombing forced Serbian troops to withdraw and end a brutal crackdown on its ethnic Albanian majority.

Since then, the number of establishments in Kosovo where trafficked women and girls are exploited has soared from 18 to more than 200, Amnesty said.

From January 2002 to July 2003, between 22 and 27 members of KFOR troops were suspected of offences related to trafficking, Amnesty quoted UNMIK figures as showing. But there was no evidence that any had been prosecuted.

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