The killing of 48 Syrian soldiers in Iraq, blamed on Syrian fighters, threatens to entangle Baghdad in the neighbouring country's civil war, a conflict in which it has sought to remain neutral.
A convoy of wounded soldiers being sent home to Syria after treatment in Iraq was ambushed by a Syrian "terrorist group" in Anbar province on Monday, killing the 48 soldiers and nine Iraqi guards, the Iraqi defence ministry said.
The ambush, the latest spillover into Iraq of the protracted conflict, seems likely to increase tensions between Shiite-led Baghdad and Sunni-majority Syrian rebels, and could heighten tensions between Iraqi Sunnis and Shiites.
Political analyst Hamid Fadhel said the Syrian civil war "is a conflict with regional dimensions," which will most affect religiously and ethnically mixed countries, such as Iraq and Lebanon.
Baghdad has consistently avoided joining calls for the departure of Syrian President Bashar al-Assad, saying it opposes arming either side and urging an end to violence on all sides.
But Monday's ambush "will increase the danger of the conflict in Syria today, and is a clear message for all Iraqis that what is happening in Syria" has moved to Iraq, Fadhel said.
John Drake, an Iraq specialist with risk consulting firm AKE Group said the ambush potentially marked a major escalation in the spillover of the conflict.
"If this was actually by Syrian rebels, it would be the biggest incursion into Iraqi territory since the start of the fighting in Syria" nearly two years ago, he said, adding there might have been at least "some support" from Iraqis.
"The fact that the (Syrian) victims entered Iraq for their safety could prompt the Syrian rebels to view Iraq and Iraqi interests as a potential threat to their effort," he said.
"This could therefore lead to a rise in intent amongst some of the more radical anti-Assad groups to attack the Iraqi state."
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Iraq is caught between conflicting pressures over Syria. Its powerful eastern neighbour, Shiite Iran, backs Assad, whose Alawite minority is an offshoot of Shiite Islam. The United States and many Arab states want to see the Syrian president step down.
Political analyst Ihsan al-Shammari said the conflict had the potential to inflame sectarian tensions inside Iraq.
"If Iraq gets involved in the Syria conflict, it will be the beginning of a major armed sectarian explosion," he said.
Official reaction to the ambush highlighted Iraq's fears of a spillover of the violence.
The defence ministry said a Syrian "terrorist group" carried out the ambush, which it termed "an attack against the sovereignty of Iraq, its land and its dignity."
Prime Minister Nuri al-Maliki's spokesman, Ali Mussawi, said: "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."
And parliament speaker Osama al-Nujaifi said that "the Iraqi army should stay away from interfering in the Syrian matter."
It is not the first time the conflict has crossed the border.
Fire from the Syrian side killed an Iraqi soldier in northern Iraq on Saturday and a young girl in western Iraq in September.
US officials have also repeatedly called on Iraq to stop allowing overflights by Iranian planes that Washington says are being used to transport weapons to Assad's forces.
On Sunday, the Syrian National Council, a key opposition group, alleged that Iraq "gave political and intelligence support to the Syrian regime."
And like other countries bordering Syria, Iraq has seen the arrival of a flood of refugees fleeing the conflict -- more than 105,000, according to the United Nations, most of whom are located in northern and western Iraq.