BAGHDAD (AP) — Al-Qaida's branch in Iraq claimed responsibility on Monday for the killing last week of 48 Syrian soldiers and nine Iraqi guards in western Anbar province.

The brazen assault suggests possible coordination between the terror network's Iraq affiliate and its ideological allies in Syria who are fighting on the side of the rebels against President Bashar Assad's regime.

The Syrian troops had sought refuge in northern Iraq during recent clashes that ended with the rebels taking over a border crossing along Iraq's northern province of Ninevah. The troops were being escorted back to Syria through another border crossing, further south, in Iraq's western Anbar province, when they were ambushed.

In a statement posted on militant websites Monday, the Islamic State of Iraq said its fighters were monitoring the movements of the soldiers as Iraqi authorities worked to transfer them secretly back across the border.

"The lions of the desert and the men of the impossible missions set up traps along the road that leads to the border exits," said the statement.

The attack started with militants detonating explosive charges on military escort vehicles assigned to protect trucks carrying the Syrian soldiers, the group said.

After that, "the fighters launched an attack from two directions using light and medium range weapons as well as rocket propelled grenades," said al-Qaida in Iraq. "Within less than half an hour the whole convoy ... was annihilated."

The account of the attack matches descriptions provided to The Associated Press by Iraqi officials in the immediate aftermath of the assault.

Syria's conflict began with anti-regime protests in March 2011 and later spiraled into civil war. The U.N. says more than 70,000 people have been killed so far.