The government closed a border crossing with Syria and sent in military reinforcements after cross-border fire killed an Iraqi soldier, the defence ministry's spokesman said on Thursday.

Mohammed al-Askari told AFP that the Yaarubiyeh crossing between eastern Syrian and the northern Iraqi province of Nineveh, near where Syrian regime forces and rebels battled on Saturday, had been closed.

"Reinforcements were sent after ... battles near the border post," Askari said, adding that the area was also under aerial surveillance.

An Iraqi soldier was killed and three people including a soldier were wounded inside Iraqi territory on Saturday during clashes on the Syrian side of the border, Askari said.

Two days later, 48 Syrian soldiers who crossed into north Iraq for medical treatment were killed in an ambush in Iraq's western Anbar province, as they were being returned to Syria.

Nine Iraqi guards also died in the attack, the defence ministry said.

Baghdad has pointedly avoided calling for the departure of Syrian President Bashar al-Assad, who is locked in a bloody civil war with rebels opposed to his regime. It has instead urged an end to violence by all parties.