One police source said after the attack on Thursday: "He was wearing an explosive belt. He approached the checkpoint as police cars were entering the ministry, then he blew himself up."
After earlier confusion, several police sources concurred on this version of the events.
Also on Thursday, hundreds of Sunni Arabs and Turkmen demonstrated in the northern oil hub of Kirkuk against the results of Iraq's general election and condemned Kurdish attempts to dominate the city.
Waving Iraqi and Turkmen flags, the protestors carried banners condemning alleged electoral fraud and calling for a national unity government.
"Long live Arabs and Turkmen", said one banner, while another read "Shame on sectarians and extremists," a veiled reference to the conservative Shia list and Kurdish parties that did well in elections.
Poll results rejected
Kirkuk, whose delicate demographic balance makes it a major flashpoint, is claimed by the Kurds as a Kurdish city, although the previous regime's Arabisation policies resulted in the settlement of many Arabs in the area.
Last week has seen thousands
protest election results
In reference to ongoing meetings between Shia and Kurdish leaders, Abdallah Mohsen al-Obedi, a Sunni Arab said: "We are demonstrating today to show our rejection of the election results and send a message to those meeting up in the north that Turkmen and Arabs know that this is an Iraqi city."
According to preliminary figures, the Kurdish Alliance took more than half the vote in the 15 December parliamentary elections, while Sunni Arab and Turkmen lists took less than 15% each.
Last week has seen thousands of mostly Sunni Arabs protesting predicted election results around the country.