A suicide bomber killed at least 21 people at the funeral of a member of Iraq's Shabak minority in the northern province of Nineveh on Saturday, security and medical sources said.

It was not immediately clear who was behind the attack.

Iraq's delicate sectarian balance has come under acute strain from the war in neighbouring Syria, which has pitted mainly Sunni rebels against a leader backed by Shi'ite Iran.

"I was attending the funeral sitting with the women when we heard a huge explosion," said Umm Mohammed, who at the funeral in Bartella, 25 km east of Nineveh's capital, Mosul.

"When we went out, we found some men either killed or injured," she said.

About 800 Iraqis were killed in acts of violence in August, according to the United Nations. That is still well below its height, when the monthly death toll sometimes topped 3,000.-Reuters