More than 30 Iraqi refugees - mostly children - have been expelled from a camp in Syria and sent back across the border, says the United Nations refugee agency.
Extra burden for refugees from Tikrit
Another 12 Iraqis were expelled from the same camp, El Hol, last week.
The UN High Commission for Refugees said Syrian authorities cited "security concerns" when asked to explain the expulsions.
The BBC's Imogen Foulkes in Geneva, says all the expelled refugees are believed to have come from Tikrit, the home town of Saddam Hussein, and it is thought Syria does not want to be seen to be harbouring anyone connected with him.
But the UN refugee agency is especially concerned that most of those expelled were children.
It said it appreciated the pressure Syria was under not to give sanctuary to Saddam Hussein loyalists, but urged that safe haven be given 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 UNHCR chief Ruud Lubbers.
The 1951 Convention on Refugees only allows for exclusion or expulsion where there is serious reason to believe that an individual has committed a war crime or a crime against humanity - not something, the agency believes, which is likely to be the case among children.
The UNHCR is also worried about an estimated 1,000 people - Iranian Kurds and other Iraqi residents - who have been stuck on the Iraqi-Jordanian border after being refused permission to enter Jordan.
According to the UN, nearly 100 people, mostly Palestinians with Jordanian spouses, were allowed to enter the Ruweished camp in Jordan on Monday.
"But the bulk of the group remain in no-man's land in increasingly difficult conditions," the agency said in a statement.
Most of them are Iranian Kurds who have fled an Iraqi refugee camp over the last week.