Gunmen killed at least 40 Iraqi and Syrian soldiers in an attack on a military convoy Monday in Iraq's western province of Anbar, police said.
The Iraqi Army convoy was transporting Syrian soldiers to a border crossing, after they had received medical treatment in Iraq, dpa reported.
Around 30 Syrian soldiers entered Iraq last week after Syrian rebels seized the Yarubiyah border crossing with the northern Iraqi city of Mosul.
Fifteen soldiers were wounded in Monday's attack, which raises concerns that Syria's civil war could engulf Iraq.
The Iraqi Defense Ministry said on its website that "a terrorist group infiltrated from Syria and carried out the deadly attack."
It warned the rival factions in the Syrian conflict "against moving their armed struggle into Iraqi territories or violating Iraq's sovereignty and borders."
Iraq says it remains neutral toward the conflict in Syria, despite the Shiite-led Baghdad government's alliance with Iran, which strong backs Syrian President Bashar al-Assad.
In Syria, government forces were trying to storm rebel-held areas in the central city of Homs, Rami Abdel Rahman, head of the Britain-based Syrian Observatory for Human Rights, told dpa. He said more than 300 people, including 116 government soldiers and some 104 rebels, had been killed in fighting there since Sunday.