Unidentified armed men killed 42 Syrians and seven Iraqis on Monday as they ambushed a convoy carrying Syrian soldiers to the border through Anbar province in western Iraq, army officers said.
The ambush, a day after a key Syrian opposition group accused Iraq of interference in Syria, threatens to entangle Iraq in its neighbour's bloody, prolonged civil war -- something Baghdad has sought to avoid.
The Syrian soldiers crossed into Iraq from the Yaarubiyeh border crossing, scene of fighting on Saturday between rebels and troops loyal to President Bashar al-Assad, Lieutenant Colonel Mohammed Khalaf al-Dulaimi told AFP.
The soldiers were first transported by Iraqi authorities to Baghdad from the northern Nineveh province, bordering Yaarubiyeh, and they were on their way to be handed over to Syrian authorities on the border with Anbar province when the attack took place, he said.
Armed men attacked the convoy from two sides with mortar rounds, automatic weapons and mines, killing 42 Syrian soldiers and seven Iraqis guarding the convoy.
Eight Syrians and four Iraqis were wounded, and three vehicles in the convoy destroyed, he said.
Major Ali Juwair al-Dulaimi from Iraq's Anbar Operations Command confirmed the toll.
The ambush was "a clear message to all Iraqis that what is happening in Syria today effectively moved to Iraq," political analyst Hamid Fadhel told AFP.
Anbar province's Sunni residents have close tribal, family and trade ties with eastern Syria, with which the province shares a long border.
And Anbar, once home to key Sunni militant strongholds, shares religious ties with Syrian rebels, who are also mainly Sunni Muslim.
Iraq's "western and northern areas close to the border with Syria have a Sunni majority and in one way or another are supportive of the armed groups fighting the Assad regime," Fadhel said.
The Monday attack comes after defence ministry spokesman Mohammed al-Askari said an Iraqi soldier was killed and three people including a soldier wounded by fire from Syria during clashes between Syrian rebel and regime forces at the Yaarubiyeh crossing.
He also said four wounded Syrian soldiers were treated at an Iraqi hospital during Saturday's fighting.
Baghdad has pointedly avoided calling for the departure of Assad, who is locked in a bloody civil war with rebels opposed to his regime, and has instead urged an end to violence by all parties.
But US officials have repeatedly called on the Iraqi government to halt Iranian overflights to Syria via Iraqi airspace that they say are transporting weapons to Assad's forces.
A key Syrian opposition group on Sunday accused the Iraqi government of intervening in Syria's conflict.
"After the Iraqi government headed by (Prime Minister) Nuri al-Maliki gave political and intelligence support to the Syrian regime... the Baghdad regime has moved on to a new level of intervention in Syrian affairs," the Syrian National Council charged.
It said Baghdad was "attacking the Syrian people, their basic rights and their territorial sovereignty."