New York City police are on high alert of possible revenge attacks amid news that American-born al-Qaida operative Anwar al-Awlaki was killed in an air strike by U.S. forces in Yemen, Reuters reported.

New York Police commissioner Ray Kelly said Friday that police are worried that al-Awlaki has followers in the city who might want to avenge his death.

We know al-Awlaki had followers in the United States, including New York City, and for that reason we remain alert to the possibility that someone might want to avenge his death, Kelly said in a statement. He was a powerful recruiter of terrorists in the United States.

Was An Influential al-Qaeda Operative

Al-Awlaki, long considered one of the most influential al-Qaida operatives wanted by the U.S., has been on the run, hiding in Yemen's remote tribal highlands. U.S. and Yemen officials say he was killed in a U.S. air strike targeting his convoy; the convoy was outside a village in the northeastern province of Jawf on Thursday, according to a Yemeni government announcement.

Born in New Mexico, the cleric and leading recrutier for al-Qaida in the Arabian Peninsula, or AQAP, a group the U.S. considers the world's most dangerous terror organization, has used his clear English, American roots and powerful speaking skills to attract many young Muslims from within the U.S. to the cause of jihad.

U.S. officials have linked al-Awlaki to at least three major terrorist incidents: the Fort Hood shootings in which 13 people were killed, the Christmas 2009 plot to blow up a U.S.-bound passenger plane and a separate plan to blow up a U.S.-bound cargo plane.

Kelly also welcomed the reported death of a second English-speaking al-Qaida operative, Samir Khan, an American of Pakistani origin. U.S. and Yemeni officials said they believed he was killed in the same drone attack.

Khan had extensive contacts in New York City and published the English language Inspire Magazine, which instructed lone wolves on how to build bombs at home, and in the most recent issue identified Grand Central Station as a target, Kelly said.