Iraq's Interior Ministry says troops have wounded the leader of al-Qaida in Iraq, Abu Ayyub al-Masri.
A spokesman for the Interior Ministry did not provide many more details about the clash near Balad, north of Baghdad. He said an aide to al-Masri was killed in the clash.
There was no immediate confirmation of the incident from the U.S. military in Iraq.
Meanwhile, in Baghdad, Iraqi and U.S. forces stepped up joint operations Thursday as part of a security crackdown. Officials say troops conducted searches and clearing operations across the city and set up checkpoints.
Despite the crackdown, three car bombs killed seven people in the capital Thursday. And in northern Iraq, south of the city of Kirkuk, gunmen killed three off-duty guards of Foreign Minister Hoshyar Zebari.
Zebari, a Kurdish politician, was not with the guards when the gunmen attacked.
In other news, a U.S. military official, Lieutenant Colonel Christopher Garver told Reuters news agency a plan to close Iraq's borders with Syria and Iran for 72 hours went into effect late Wednesday.
And Iraq's President Jalal Talabani said Thursday Iraq's biggest Shi'ite militia, the Mahdi Army, ordered some of its members to leave Iraq temporarily.
The Mahdi Army is loyal to radical Shi'ite cleric Moqtada al-Sadr, who Iraqi and U.S. officials say is already in Iran.