Tensions ran high in eastern Iraq on Friday between Kurdish and Shi'ite fighters, highlighting divisions hampering efforts by the U.S.-backed government to blunt the momentum of Islamic State militants.
There were conflicting reports on what transpired in Diyala province after Kurdish peshmerga fighters attempted to dig a trench to separate two towns there, Jalawla and al-Saadiya, police sources said.
Jalawla is held by Kurds while al-Saadiya is controlled by Shi'ites.
A police official said five people were killed after clashes erupted between the two sides competing for territory in several parts of Iraq, even though they have joined forces against Islamic State in the past.
But Mahmoud Sangawi, the senior Kurdish frontline commander in the area, said the forces only fired over each other's heads and the situation was tense.
"We don't have a problem with them, but we won't accept for them to attack us," he said.
There have been skirmishes in the past between Kurdish and Shi'ite forces, both seen as critical to efforts to contain Islamic State.
The jihadist group has seized a third of Iraq over the past year, presenting the most serious security challenge since the fall of Saddam Hussein in 2003.
Islamic State's drive, ultra-hardline views and ambitions to create a self-sustained caliphate where any opponents are executed or beheaded have exacerbated a sectarian conflict.
On Wednesday, President Barack Obama ordered the deployment of 450 more U.S. troops to the Sunni heartland of Anbar to advise and assist fragile Iraqi forces being built up to try to retake territory lost to Islamic State.
The plan to expand the 3,100-strong U.S. contingent in Iraq and open a new operations center closer to the fighting in Anbar marks an adjustment in strategy for Obama, who faces mounting pressure to do more to blunt the momentum of the insurgents.
Obama refuses to send troops into combat or to the front lines in Iraq.
The focus now is on devising an effective plan to retake Anbar's provincial capital of Ramadi, which insurgents seized last month on an operation that highlighted the shortcomings of the Iraqi army.
(Reporting by Baghdad bureau and Isabel Coles in Erbil; Writing by Michael Georgy; Editing by Tom Heneghan)