Finance Minister Rafe al-Essawi survived the blast Sunday in Salahuddin province north of Baghdad, The Washington Post reported.
Essawi, text-messaging, did not say whether he thought the attack was random or specific to his convoy.
"We will send a letter to the Ministry of Interior to investigate," he said in a message.
Col. Jassim Abdulla, a deputy police chief in Salahuddin, said Essawi was returning to his home to Baghdad when the attack occurred. Abdulla said three of Essawi's bodyguards were hospitalized in Tikrit.
Further details about the incident were unavailable, the Post said.
Essawi, considered a moderate, is part of the Iraqiya political bloc supported by Sunnis and including Shiites. The alliance has criticized Prime Minister Nouri al-Maliki, a Shiite, who has taken action to consolidate his power since the U.S. military left Iraq.
Shiite-controlled security forces recently accused another Sunni official, Vice President Tariq al-Hashimi, of running a hit squad. Al-Hashimi fled to Kurdistan. Maliki has demanded that the vice president return to Baghdad to be tried.