Two Austrian soldiers stationed with the UN force on the Golan Heights were shot and wounded in Syria while their convoy was travelling to Damascus airport on Thursday, the defence ministry in Vienna said.
The pair, whose lives were not in danger, were part of the Austrian contingent of the United Nations Disengagement Observers Force (UNDOF) on the Golan Heights and were travelling to Damascus airport to fly back to Austria after their tour of duty, the ministry said.
Two more soldiers in the Austrian convoy were lightly injured by fragments, it added.
It was unclear whether they were shot by Syrian government forces or rebels fighting to overthrow President Bashar al-Assad's regime, according to a ministry spokesman.
The United Nations confirmed the incident, saying it occurred "in an area of Damascus where military operations between the Syrian armed forces and armed members of the opposition were taking place."
"The Secretary-General remains deeply concerned about the evolution of the conflict in Syria," the statement from Ban Ki-moon's spokesman said.
"As today's incident illustrates, the ongoing clashes between the Syrian armed forces and the armed members of the opposition affect UNDOF's operations and pose a serious risk to United Nations personnel on the ground.
"Safety and security of United Nations personnel is of the highest priority for the United Nations," the statement added.
One soldier, aged 25, was shot in the arm and his 53-year-old in the shoulder, but both were quickly treated by an accompanying doctor and the convoy then arrived at the airport.
Foreign Minister Michael Spindelegger and Defence Minister Norbert Darabos condemned the attack, adding they would file a loud protest with the UN Security Council.
"That Austrian peacekeepers are shot at must be condemned in the strongest terms and demands appropriate consequences," they said in a joint statement.
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"The Austrian government will do everything it can, along with the UN, to make sure this incident is resolved clearly."
Spindelegger had instructed the Austrian embassy in Damascus to file a protest with the Syrian government.
"Syria is responsible for the safety of our UNDOF soldiers and must ensure that they can fulfil their international mandate," he said.
The Syrian ambassador in Vienna was also summoned to the foreign ministry on Thursday to give an explanation and he expressed regret over the incident, according to a ministry statement.
This was the first such shooting of UN troops to take place in Syria, according to Austrian authorities.
In Syria, state television, quoting a foreign ministry source, blamed the shootings on rebels.
About 100 Austrian peacekeepers were flown out of Damascus Thursday evening and were expected in Vienna overnight after completing their six-month stint in Syria. The two injured soldiers were meanwhile brought to a hospital in Israel for further treatment.
A further 70 Austrian UN troops who arrived Thursday in the Syrian capital on their way to the Golan Heights, were to stay at the airport until the morning for safety reasons, according to the defence ministry.
The situation there was quiet at the moment, it said.
Syrian troops mounted an assault on rebels near Damascus on Thursday, closing off the road to the airport before later securing it, authorities said, amid a widespread telecommunications outage.
Austria contributes some 370 soldiers to UNDOF on the Golan Heights, near Syria's border with Israel. The situation in that region was currently calm, the defence ministry said.
Israel captured the Golan from Syria during the 1967 Six Day War and annexed it in 1981, in a move never recognised by the international community. The Security Council established UNDOF in 1974 to enforce a ceasefire between Israeli and Syrian forces.