There are reports that a Turkish lorry driver was shot dead and two other men were wounded by US troops after failing to stop at a checkpoint near Baghdad.
Turkish television said the lorry was travelling to the Iraqi capital from Fallujah, carrying prefabricated housing units destined for American soldiers.
The US embassy in Ankara said it could not confirm the shootings.
Earlier in Baghdad, there was a large explosion near the country's central bank.
It is not believed there were any casualties, but two bank employees and a security guard were injured.
A mini-bus and a larger bus were found at the site of the blast.
There have been an increasing number of car bombings in Iraq ahead of the transfer of sovereignty due to take place at the end of the month.
