At least 17 people were killed and more than 50 wounded Saturday, when a suicide bomber blew up his car outside the Iraqi National Guard headquarters in the northern city of Kirkuk.

The attack is the latest in a wave of bombings and drive-by shootings aimed at Iraq's police and security forces.

Authorities say the bomb exploded at the rear of the headquarters building, where many of the victims were waiting in line to apply for jobs.

In Baghdad, several large explosions rocked the highway leading to the airport. Initial reports say the blasts targeted a U.S. military convoy. There are no immediate reports of casualties.

In further violence, at least four bodyguards were killed in an apparent assassination attempt on a senior official of Iraq's state-run Northern Oil Company, Mohammed Zibari. The official escaped unharmed.

In the southern city of Basra, British troops clashed sporadically for a second day with supporters of radical Shi'ite cleric Moqtada al-Sadr. At least five people were wounded.