The EU mission in Kosovo has launched a preliminary investigation into allegations Kosovo prime minister Hashim Thaci once led a ring trafficking in human organs.
The EU mission, known as Eulex, cited a Council of Europe reported in December that suggested Mr Thaci was once the "boss" of a criminal underworld behind the alleged organ trade during the 1998-99 war against Serbia, EU mission spokesman Karin Limdal said.
Mr Thaci has denied the claims.
The mission said it took those allegations "very seriously" and was "ready, willing and able to assume responsibility" for a judicial process, Ms Limdal said in a statement.
The December report alleges that civilians detained by the now-disbanded rebel Kosovo Liberation Army were shot dead to sell their kidneys on the black market at the time.
Mr Thaci, who was a leader of the guerrilla group in the 1998-1999 war against Serbia, has claimed the allegations were aimed at damaging Kosovo's image internationally.
He and other Kosovo leaders have called for an investigation.
EU officials appealed for those who could help the investigation to come forward and present evidence.
"As a rule of law mission, we work on the basis of fact and evidence. Without evidence, prosecutions cannot take place," the EU statement said. "If we receive this information, our prosecutors are ready to follow up immediately."