An American-born al Qaeda operative has been arrested in Karachi, Pakistan, according to security officials. But there are conflicting reports about the man's identity.

Citing government and military sources, The Associated Press reported Sunday that 31-year-old American-born Adam Gadahn had been detained.

Gadahn is a spokesperson for al Qaeda who has appeared in several of the group's propaganda videos. He was born in California but moved to Pakistan 12 years ago. He is known by a number of aliases including Yahya Majadin Adams and Azzam al Amriki.

Later in the day, the New York Times reported that the arrested American was in fact Abu Yahya Mujahdeen al Adam, a Pennsylvania native who officials suspect of working with al Qaeda's operations arm. The newspaper cited American and Pakistani officials in its report.

Local media first broke news of the arrest on Sunday.

A number of senior militants have recently been captured in Pakistan, including al Qaeda members and top leaders of the Afghan Taliban.

Several arrests have been made in the southern city of Karachi, which has become a financial and logistics centre for some militant groups.