Yugoslav officials say Serbian Deputy Prime Minister Momcilo Perisic was released by military police Saturday, two days after he was detained on suspicion of spying for the United States. Mr. Perisic was set free after military prosecutors questioned him in a case that has led to diplomatic tensions between the United States and Yugoslavia.

The Serbian deputy prime minister was released after undergoing questioning on suspicion of passing secret documents to a U.S. diplomat. Mr. Perisic was detained Thursday by Yugoslav military police along with the American official in a Belgrade restaurant.

The U.S. Embassy in Belgrade said the diplomat, identified by Yugoslav officials as John David Neighbor, was released after 15 hours, but Mr. Perisic was held for nearly two days.

U.S. and Yugoslav government officials have condemned the military for detaining Mr. Perisic - a former general - and the alleged mishandling of the U.S. diplomat during his detention.

Yugoslav media speculated Mr. Perisic may have been involved in providing evidence against former Yugoslav President Slobodan Milosevic, on trial on war crimes charges before the United Nations War Crimes Tribunal in The Hague.

Military sources initially said the documents in Mr. Perisic's possession could incriminate Mr. Milosevic for his alleged role in war crimes committed by troops loyal to him in Kosovo, Bosnia and Croatia. But they have also cautioned that the evidence link to the former Yugoslav leader was unclear.

Mr. Perisic served as Yugoslavia's chief of staff during the conflicts in Croatia and Bosnia, and he was sentenced in a Croat court in his absence to 20 years in prison for allegedly ordering the shelling of the Adriatic towns of Sibenik and Zadar. However, Mr. Perisic was fired by then-President Milosevic in 1998 for criticizing the military campaign in Kosovo against ethnic Albanians.

After his ouster, Mr. Perisic formed the opposition Movement for Democratic Serbia, which played a major role in Mr. Milosevic's ouster in October 2000.

The arrests of Mr. Perisic and the U.S. diplomat have led to new tensions between the prime minister of Yugoslavia's main republic of Serbia, Zoran Djindjic, and the Yugoslav President Vojislav Kostunica, to whom the army owes at least nominal allegiance.

Mr. Djindjic has accused the Yugoslav military of fabricating a scandal to embarrass the country, and said army intelligence, which informed neither its superiors nor top Yugoslav politicians of the arrests, was out of control.

But Yugoslav President Kostunica, who has refused to fire several officers appointed by Mr. Milosevic, has defended the army's actions. On Saturday he described the detentions of both the U.S. diplomat and the deputy prime minister as "being within legal limits."

Analysts say the arrests have underlined the growing rift between Mr. Kostunica and Mr. Djindjic over the pace and direction of political and economic reforms. Mr. Djindjic, who is considered to be more pro-Western, was instrumental in Mr. Milosevic's extradition to the U.N. court, but President Kostunica said he should first have been tried in Yugoslavia.