A suicide bomber has killed 10 people in an attack on a joint US-Iraqi base in the Iraqi town of Baquba which led to three more "friendly fire" deaths.
The blast injured Iraqi and US personnel at the jointly run base
Eight policemen died in the explosion along with a US soldier and a contractor, according to US military and Iraqi police reports.
And three members of an Iraqi special forces unit in the area were killed in error by US troops, Iraqi police added.
Elsewhere, an Iraqi minister said she had survived an assassination attempt.
The explosion in Baquba, 50km (30 miles) north-east of Baghdad, occurred in a dining area in the Provincial Joint Co-ordination Centre.
According to the police, US soldiers responding to the blast apparently mistook the special forces soldiers for insurgents and opened fire.
Environment Minister Narmine Othman, an Iraqi Kurd, said on Tuesday she had survived an assassination attempt a day earlier by gunmen who attacked her convoy.
The minister was travelling through the Oudhaim region, between the northern city of Kirkuk and Baquba, when attackers opened fire, injuring three of her guards.
"The cowardly act will not deter me from doing my job towards Iraq and fellow citizens," the AFP news agency quotes Ms Othman as saying.
Two Iraqi policemen were also reported killed in a clash with insurgents during a raid in Haydariya, north of the city of Najaf.
Iraq's fledgling security services have been a frequent target for insurgents.