From the Washington Post –

KARACHI, Pakistan — The American-born spokesman for al-Qaida has been arrested by Pakistani intelligence officers in the southern city of Karachi, two officers and a government official said Sunday, the same day Adam Gadahn appeared in a video urging U.S. Muslims to attack their own country.

The arrest of Gadahn is a major victory in the U.S.-led battle against al-Qaida and will be taken as a sign that Pakistan is cooperating more fully with Washington. It follows the recent detentions of several Afghan Taliban commanders in Karachi.