BELGRADE, Serbia (AP) - The state security chief for the late Yugoslav President Slobodan Milosevic was returned to detention at the U.N. war crimes tribunal Monday, despite claims by his defense lawyers that he is gravely ill, Serbian media reported.

Jovica Stanisic was flown to the Hague, Netherlands, together with his former top associate, Franko Simatovic, the official Tanjug news agency reported.

The two were charged in 2003 in connection with war crimes committed by Serbian secret service troops during the wars in Croatia and Bosnia in the 1990s.

Stanisic and Simatovic were temporarily released in 2004 and allowed to return to Belgrade until the start of their trial at the court in the Hague.

Stanisic's lawyers have demanded that the proceedings against him be halted, saying he is too ill to stand trial. The prosecution has said that he was healthy enough to be tried, news organizations in Serbia have reported. The final decision will be made by the court.

Stanisic is known to have suffered from a chronic intestinal disease.

Stanisic was a key associate of Milosevic during the wars in Croatia and Bosnia. He and Simatovic are believed to have organized the paramilitary units that fought alongside the Serbs in the two former Yugoslav republics.