The U.N. High Commissioner for Refugees said Syrian security forces entered the El-Hol refugee camp in the country's northeast on Monday and removed nine adults and 23 children. The group was believed to have been taken to the Iraqi side of the border.
Another 12 Iraqis were expelled from the camp on April 13.
The U.N. agency said Syrian authorities cited "security concerns" when asked to explain the expulsions. The agency said it appreciated the pressure Syria is under not to give sanctuary to Saddam loyalists but urged it to give safe haven to asylum seekers.
"We are aware of the complexity of the situation, but we insist that the basic norms of international refugee law ... be observed by all concerned parties," said refugee agency chief Ruud Lubbers.
The 1951 international refugee convention says governments can refuse asylum if they have solid reason to believe an individual has committed war crimes or a serious nonpolitical crime.
In Damascus, U.N. refugee official Abdelhamid El Ouali said there were now 128 refugees from Iraq in the El-Hol camp, including 27 who took refuge in Syria after the 1991 Gulf War. The camp also is home to 26 Palestinian workers who fled the recent war in Iraq, he said.
El Ouali did not comment directly on the expulsions, but said, "All Iraqis have the right to stay in Syria."
The agency also said it was worried about an estimated 1,000 refugees and other residents of Iraq who have been stuck in a no man's land between Iraq and Jordan.
On Tuesday, U.N. officials said 270 people from the group -- Palestinians with Jordanian spouses, Iraqis and Syrians -- had been permitted to enter a U.N. refugee camp at Ruweished, Jordan. But the refugee agency said the bulk of the group remains and faces "increasingly difficult conditions."
Most of the group are Iranian Kurds who had lived at the Al Tash refugee camp in Iraq for up to two decades. Before the war, Al Tash sheltered more than 12,000 Iranian Kurdish refugees.
Ahead of the war in Iraq, the United Nations estimated that 600,000 people might flee the country. Although only a trickle ended up leaving, Lubbers said this month that his agency did not plan to lower its estimate yet because people often flee even after political settlements have been reached.