REUTERS - A car bomb in a market killed at least four people and wounded 50 in the violent northern Iraqi city of Mosul on Saturday, police said.

Mosul and surrounding Nineveh province are among the last remaining strongholds of insurgents in Iraq, who have stepped up bombings to test Iraqi security forces since the U.S. military pulled out of Iraqi cities at the end of last month.

The latest bomb struck an area of eastern Mosul largely inhabited by the minority Shabak ethnic group, who speak Kurdish and profess the Shi’ite version of Islam.

Many recent militant attacks seem aimed at stoking ethnic and sectarian tensions in the country, which is still recovering from a wave of sectarian violence in 2006/7 that brought Iraq to the brink of all out civil war.

On Thursday, two suicide bombings in Tal Afar, not far from Mosul, killed 34 people and wounded around 60. A spate of attacks this month have underscored doubts many Iraqis have about the ability of their own security forces to protect them.