Armed men from Syria carried out an ambush in western Iraq on Monday killing 48 unarmed Syrian soldiers being transferred to the border and nine Iraqi guards, the defence ministry said.
The ambush in Anbar province, a day after a key Syrian opposition group accused Iraq of interfering in Syria, threatens to entangle Baghdad in its neighbour's civil war -- something it has tried hard to avoid.
"This confirms our fears of the attempt of some to move the conflict to Iraq, but we will face these attempts by all sides with all of our power," Ali Mussawi, Prime Minister Nuri al-Maliki's spokesman, said of the ambush.
The defence ministry said in an online statement that the ambush was carried out "by a terrorist group that infiltrated into Iraqi territory coming from Syria," and put the death toll at 48 Syrian soldiers and nine Iraqi guards.
It said a number of unarmed and Syrian soldiers wounded in fighting had fled to Iraq for medical treatment and were being transferred to Al-Walid border crossing to be returned to Syria through "official channels."
But they were ambushed on the way, in what the ministry termed "an attack against the sovereignty of Iraq, its land, and its dignity, and a clear violation of human rights, as (the soldiers) were wounded and unarmed."
The ministry also issued a warning to all sides in the conflict in Syria, where President Bashar al-Assad is locked in a bloody, prolonged civil war with rebels, "against moving their armed conflict to Iraqi territory and violating Iraq's borders."
Political analyst Hamid Fadhel said the ambush was "a clear message to all Iraqis that what is happening in Syria today effectively moved to Iraq."
Anbar province's Sunni residents have close tribal, family and trade ties with eastern Syria, with which the province shares a long border.
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Once home to key Sunni militant strongholds, Anbar also has religious affiliations with the mainly Sunni rebels in Syria fighting the regime.
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.
Monday's attack came after the defence ministry said an Iraqi soldier was killed and three people wounded by fire from Syria during clashes between Syrian rebel and regime forces at the Yaarubiyeh crossing, which leads to Nineveh province in north Iraq.
Defence ministry spokesman Mohammed al-Askari also said four wounded Syrian soldiers were treated at an Iraqi hospital during the fighting on Saturday.
Baghdad has pointedly avoided calling for Assad's departure of Assad, and it 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 through 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 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 National Council charged.
It said Baghdad was "attacking the Syrian people, their basic rights and their territorial sovereignty."