By Serhad Shaker and Ibrahim Salih

NINEVEH, Iraq

At least 15 Iraqi civilians were killed on Sunday when a warplane struck their house in western Mosul, according to an Iraqi rights activist.

"The victims were taking refuge inside the house when the plane struck the building," Mohamed Fadel told Anadolu Agency.

He said five other people were injured in the attack.

It remains unclear whether the airstrike was carried out by an Iraqi or a U.S.-led coalition plane.

Meanwhile, five Iraqis trying to flee western Mosul were executed by Daesh militants.

"Their bodies were dumped on the road leading to the positions of Iraqi security forces" in Mosul, federal police officer Sabhan Ali said.

He said Daesh terrorist group always dumps the bodies of executed civilians "in an attempt to scare others from fleeing the city".

In October, the Iraqi army -- backed by U.S.-led coalition airstrikes and local allies on the ground -- began a wide-ranging operation to retake Mosul, Daesh’s last bastion in northern Iraq, which the terrorist group overran in 2014.