The bomber drove a vehicle packed with explosives up to a military checkpoint in Mosul, 390 km (240 miles) north of Baghdad, and detonated it, killing eight people and wounding 18, among them soldiers.
"The blast destroyed everything. It looks like there was nothing here before the explosion," said a policeman at the scene who declined to be identified because he was not authorised to speak to the media.
In a separate incident in Mosul, gunmen using silenced weapons killed the bodyguard of a Kurdish member of the city's provincial council and three others, police said.
A surge in violence since the withdrawal of U.S. troops in late 2011 is stoking fears of a return to the sectarian strife that killed tens of thousands of Iraqis in 2006 and 2007.
Prime Minister Nouri al-Maliki, a Shi'ite Muslim, is facing mass protests by disenchanted Sunnis and is at loggerheads with ethnic Kurds who run their northern region autonomously from Baghdad.
The prospect of provincial elections is hardening the divisions as political leaders appeal to their constituencies with hostile and uncompromising rhetoric.
The conflict in neighbouring Syria, where mainly Sunni rebels are fighting to overthrow a leader backed by Shi'ite Iran, is also whipping up sectarian tensions in Iraq and across the wider region.
© Thomson Reuters 2013