PARIS — A special European Union prosecutor said Tuesday that senior members of the Kosovo Liberation Army engaged in a campaign of persecution against ethnic Serbs after the 1998-99 Kosovo war, and said evidence suggested that the armed group had targeted a number of individuals after the war to harvest and sell their organs.

Kosovo declared independence from Serbia on Feb. 17, 2008, almost a decade after NATO bombs helped eject the former Serb strongman Slobodan Milosevic from Kosovo, ending a brutal civil war against the ethnic Albanian majority. But regional reconciliation has been hampered by accusations that senior members of the Kosovo Liberation Army, known by its initials K.L.A., have not been held fully accountable for suspected war crimes.

A European Union task force was set up in September 2011 under the leadership of Clint Williamson, an American diplomat who served as the war crimes envoy in the administrations of George W. Bush and President Obama. The task force was created after a Council of Europe report accused Kosovo’s prime minister, Hashim Thaci, the former commander of the K.L.A. of having led a “mafialike” group that smuggled human organs, weapons and heroin during and after the war. Mr. Thaci has strenuously rejected those accusations and the Kosovo government at the time called them “despicable.”

While refusing to describe whether Kosovo’s current political leadership was potentially implicated in war crimes, Mr. Williamson said at a news conference on Tuesday in Brussels that the suspects included “individuals at the most senior levels of the K.L.A.”