BAGHDAD (AP) — A string of car bomb attacks in and around Baghdad killed 17 people and wounded dozens today, deepening fears of an increase in violence as sectarian tensions simmer in Iraq.

Although there was no immediate claim of responsibility, blame is likely to fall on Sunni insurgents such as al- Qaida’s local franchise. The group often uses indiscriminate car bombs to sow fear among Iraq’s Shiite majority and undermine the government’s authority.

The killing began in the morning when a parked car exploded in Mahmoudiya, about 20 miles south of the Iraqi capital, targeting a security checkpoint there. The explosion killed five, including two soldiers who were manning the checkpoint, and wounded 15 people, according to police.

Then, a suicide car bomb struck near a checkpoint in the northern Baghdad suburb of Taji, killing seven people and wounding 26.