PARIS — The president of Serbia, Boris Tadic, lashed out at organized crime and its corrosive effect on the Balkans in a speech Wednesday, pressing for an international investigation of human organ trafficking in Kosovo and broad protection for witnesses. He made his comments in Strasbourg before the Parliamentary Assembly of the Council of Europe, which on Tuesday adopted an investigative report that has roiled the leadership in Kosovo. It alleged that Serb prisoners were killed at the end of the Kosovo conflict in 1999 to harvest organs for transplant for an organized crime group, Drenica, with ties to the...