PARIS  A two-year international inquiry has concluded that the prime minister of Kosovo led a clan of criminal entrepreneurs whose activities included trafficking in organs extracted from Serbian prisoners executed during the Kosovo conflict in 1999.

The inquiry, prepared for the Council of Europe, names the prime minister, Hashim Thaci, as the boss of the Drenica Group, an organized crime network that flourished in Kosovo and Albania after the war and exerted control over numerous rackets, including the heroin trade, and six secret detention centers in Albania, some used in a black market in human organs.

Kosovo denounced the findings of the inquiry, which began to leak late Tuesday, ahead of the official release on Thursday. One official called the report slanderous and timed to harm Mr. Thaci, whose party recently won the first parliamentary election in Kosovo since it declared independence from Serbia.

The report did not explicitly describe any role of Mr. Thaci in the organ trafficking network.

The Council of Europe said the investigating team that gathered evidence used foreign intelligence analysts, international organizations, former fighters, logistics operatives and victims. The report cites some names but withholds others, saying local witnesses feared for their lives.