BAGHDAD (AP) — Sunni lawmakers pulled out of talks on forming a new Iraqi government after militants attacked a Sunni mosque in a volatile province outside Baghdad during Friday prayers, killing at least 64 people.

It was not immediately clear if the attack was carried out by Shiite militiamen or the Islamic State extremist group, which has been advancing into the ethnically and communally mixed Diyala province and has been known to kill fellow Sunni Muslims who refuse to submit to its leadership.