Described as "one of the most wanted people" in northern Iraq, Mullah Kamel al-Assawadi was arrested after he allegedly tried to pass an Iraqi checkpoint, a US military statement said on Wednesday.
One of al-Zarqawi's alleged regional secretaries was also detained in Baquba, north of Baghdad.
"Assawadi was questioned by an Iraqi soldier at a checkpoint close to Balad," 70km north of Baghdad, said the statement, without giving details of the arrest.
Described as one of al-Zarqawi's top lieutenants, al-Assawadi had on him various identity papers as well as dollars with which he tried to buy the soldier's silence, claimed the statement.
The Iraqi Defence Ministry also announced the arrest in Baquba on Tuesday of al-Zarqawi's secretary for Diyala province, Agha Omar, without providing further details.
News of the arrests came a day after an Internet statement issued by al-Zarqawi's group said the Jordanian-born al-Qaida leader had been wounded.
The United States has put a $25 million price on his head for his alleged involvement in Iraqi fighting.
The Iraqi government had no comment about the reported wounding of al-Zarqawi.