The Guardian - Human Rights Watch and a UN refugee agency have expressed concern that Lebanon is blocking Palestinians fleeing Syria from entering the country.
UNRWA, the UN agency for Palestinian refugees, said it was "concerned about the increased restrictions on Palestine refugees fleeing the conflict in Syria from entering Lebanon".
Its spokesman, Chris Gunness, said in a statement: "We are monitoring the situation on the border carefully and have been given assurances by the Lebanese authorities that these restrictions are temporary."
Human Rights Watch criticised Lebanon for refusing entry for Palestinians from Syria and forcibly returning them to the war-torn country. It accused Beirut of arbitrarily denying entry, and documented the deportation of around 40 Palestinians accused of having forged documents.
Beirut has not announced a blanket ban on the entry of Palestinians from Syria, but government sources confirmed there was a general policy to keep out Palestinians fleeing the conflict.
Speaking on condition of anonymity, one source said the government felt Palestinian refugees registered in Syria should stay there, pointing out that Lebanon already had more than one million Syrian refugees.
HRW said the Lebanese government was violating international law by sending civilians back to an active war zone. "The Lebanese government should urgently rescind its decision to bar Palestinians from Syria from entering Lebanon. Lebanon is turning people back without adequately considering the dangers they face."
The group said Palestinians seeking to enter Lebanon from a crossing with Syria had been arbitrarily denied entry over the weekend.
A security official told AFP that 41 people, many of them Palestinians, were returned to Syria after they were caught trying to fly out from Beirut airport using fake visas. "Eight were allowed to stay because they have Palestinian Lebanese relatives here, or other documentation that allows them to be here," the official said.
Among the more than one million refugees from Syria registered in Lebanon are around 52,000 Palestinian Syrians. Once numbering 500,000 in Syria, Palestinians have been targeted by both sides in the war, making them one of the country's most vulnerable groups, rights groups say.
Lebanon is home to around 422,000 Palestinian refugees, whose presence in the country remains a source of tension. Unlike Jordan and Turkey, which also host a large number of Syrian refugees, Lebanon refuses to set up camps for people fleeing Syria's war. Some politicians have cited the semi-permanent status of Palestinian refugee camps in Lebanon dating back to the 1948 creation of Israel as the reason why Lebanon does not want more camps.
The international community has praised Lebanon, which has a population of four million, for absorbing so many of those fleeing Syria.
HRW urged foreign governments to better assist Beirut in hosting refugees. "The Lebanese government is bearing an incomparable burden with the Syrian refugees crossing its borders, but blocking Palestinians from Syria is mishandling the situation," said HRW's deputyMiddle East and North Africa director, Joe Stork.