Clashes between Iraqi border police and gunmen who crossed from Syria into western Iraq killed a policeman and wounded five on Saturday, an officer said.
The gunmen travelling in five four-wheel-drive vehicles crossed into Iraq's Anbar province about six miles (10 kilometres) from the Al-Waleed border crossing with Syria, Major Shihab Taha of the border police said.
Clashes broke out between the gunmen and the border police inside Iraq, killing one policeman and wounding five, Taha said, putting the number of gunmen killed at two.
The toll could not be confirmed, however, with the gunmen taking the bodies with them when they returned to Syria.
Iraq has sought to publicly avoid taking sides in the civil war between Syrian President Bashar al-Assad's regime and rebels seeking his ouster, but the conflict has spilled over the border on several occasions.
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In June, a border guards officer said Syrian rebels had opened fire on two Iraqi border posts, killing a guard and wounding two.
In March, armed men ambushed a convoy carrying Syrian soldiers who had entered Iraq for medical treatment on their way back to their home country, killing 48 Syrians and nine Iraqi guards, the defence ministry said.
The day before that, an Iraqi soldier was killed and three people including a soldier wounded inside northern Iraq by fire exchanged between regime forces and rebels in Syria.
The United States has also repeatedly called on Iraq to stop flights allegedly carrying arms from Iran to the Syrian regime.
Iraqi Foreign Minister Hoshyar Zebari said in an interview published on Saturday that Iraq did not have the means to prevent any arms transfers.
"Last September we started to inspect Iranian and Syrian planes at random. We have found non-lethal materials, like equipment, medicine and food," Zebari told Asharq al-Awsat newspaper.
"In all honesty, those planes might be carrying other stuff, but we have neither the deterrent means, nor the air defences and fighter jets to prevent... arms shipments," he said.