Reports of the incident were fragmentary and Turkish authorities said they were still trying to establish what had happened. Some of the shaken travelers said the attackers appeared to be Syrian soldiers.

Turkey's state news agency Anatolia said a driver and a pilgrim were hit when the attackers strafed two of the buses returning to Turkey on the road between the cities of Homs and Hama in western Syria in the early hours of Monday morning.

Cemil Karli, 50, said he had been shot in the stomach and the leg.

"We were traveling in a convoy of around eight or nine buses. First a red car appeared and there were four people inside. First they started shooting from there," Anatolia quoted Karli as saying.

"When they realized we were going to carry on driving, four other people appeared up ahead and started shooting. Their gunfire did a lot more damage."

Karli said windows in the bus were shattered by bullets and passengers threw themselves on top of each other in the aisle.

"This is how we saved our lives. Our bus drove at speed through the armed group and drove without stopping all the way to the Cilvegozu border gate," he said, referring to one of the crossings in Turkey's 910-km border with Syria.

Passengers interviewed by private news agency Dogan said they had been told to get off their bus by up to eight men in Syrian Army uniforms at a checkpoint.

"They were hidden in their hide-outs ... these were soldiers, these were not civilians, their flags were there," one man said.

One of the soldiers said 'come, come', he wanted to get me inside, I didn't go inside.

"I had nothing in my hands, there were seven or eight of them. He cocked his gun at me and said 'put your hands up' ... I shouted for everyone to run, we ran and they started firing at our backs. God saved us," he said.

"We have returned from death. We have returned from death," said another middle-aged male passenger, sobbing.

Dogan showed television images of a bus with one of its windows smashed, after it had crossed back into Turkey.

Meanwhile, the International Committee of the Red Cross said Syria has yet to grant officials from the group permission to visit most prisons in the country, despite months-long efforts to secure humanitarian access.

The ICRC said its president, Jakob Kellenberger, stood ready to travel to Damascus for a third time to press authorities on the issue.