BAGHDAD — A suicide bomber set off a car bomb today at a checkpoint leading to the Iraqi Interior Ministry, killing six people and injuring 32 others, officials said.

The attack followed a series of bombings last week that killed up to 70 people in a single day, increasing fears about Iraq’s future after U.S. troops withdrew this month.

Two police officers said the bomber struck during morning rush hour, hitting one of many security barriers set up around the ministry’s building. Four policemen were among the dead, they said.

Two doctors at nearby hospitals confirmed the causality figures. All spoke on condition of anonymity because they were not authorized to release information.

No one has claimed responsibility, but suicide attacks are the hallmark of the al-Qaida in Iraq terror group.

U.S. and some Iraqi officials have warned of a resurgence of Sunni and Shiite militants and an increase in violence after the full U.S. troop withdrawal.