An alleged U.S. helicopter raid on a settlement in Syrian territory that left at least eight people dead has sparked furious reaction. Damascus has condemned the move as “serious aggression”.

Four U.S. military helicopters crossed the Iraqi-Syrian border on Sunday shortly before sunset and attacked the Sukkariyeh farm near the town of Abu Kamal, according to a Syrian government statement. The attack left at least eight people dead, including four children.

The Syrian Foreign Ministry summoned top U.S. and Iraqi envoys to the country to protest against the attack.

“Syria condemns this aggression and holds the American forces responsible for this aggression and all its repercussions. Syria also calls on the Iraqi government to shoulder its responsibilities and launch an immediate investigation into this serious violation and prevent the use of Iraqi territory for aggression against Syria,” the government statement said.

The U.S. has so far neither confirmed nor denied the raid. An unnamed military official told Associated Press that the attack had targeted an Al Qaeda linked network that helped foreign fighters infiltrate into Iraqi territory through Syria. He said the Americans have been unable to block the inflow because Syria was out of their reach.

The attack mirrors U.S. border policy in Afghanistan where Washington sanctioned raids into Pakistani territory against Taliban insurgents. Islamabad said the U.S. had violated its sovereignty by carrying out these attacks.