BAGHDAD (AP) — Prominent Shiite leaders pushed Thursday for the removal of Iraqi Prime Minister Nouri al-Maliki as parliament prepared to start work next week on putting together a new government, under intense U.S. pressure to rapidly form a united front against an unrelenting Sunni insurgent onslaught.

Increasingly, the Shiite al-Maliki’s former allies believe he cannot lead an inclusive government that can draw minority Sunnis away from support for the fighters who have swept over a large swath of Iraq as they head toward the capital, Baghdad. In a further sign of Iraq’s unraveling along sectarian lines, a bombing on Thursday killed 12 people in a Shiite neighborhood of Baghdad that houses a revered shrine, and police found the bullet-riddled bodies of eight Sunnis south of the capital.