State Department spokesman Philip Crowley said the U.S. embassy vehicle was attacked in the Sanaa suburb of Hada. The vehicle was said to have been parked in front of a restaurant frequented by Westerners when the grenade was thrown.

"We have no further information for you at this time as an investigation is currently underway," Crowley said.

Yemeni officials said the Jordanian detainee was believed to have been linked to Al Qaida in the Arabian Peninsula. They said the detainee, a resident of Yemen, was found with a false identity.

Over the last two years, Al Qaida claimed responsibility for several attacks on the British and U.S. embassies in Sanaa. In October 2010, AQAP said it had placed two parcel bombs on cargo aircraft headed for the West. The bombs were found and nobody was injured.

AQAP was said to have expanded its presence in Yemen and the rest of the Gulf in 2010, with at least 15 Yemeni soldiers killed or injured in attacks over the last three days. A leading AQAP commander was identified as Fahd Al Quso, wanted for the bombing of the USS Cole in Aden in 2000 and released from a Yemeni prison seven years later.

"We will not give up our religion and the principles that we hold in our hearts," Al Quso told the Saudi-owned A-Sharq Al Awsat daily. "This is unlikely."

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