Yemen said Awlaki was killed in Jawf province, along with several of his associates - US officials said US drones had carried out the attack.

Awlaki, who was of Yemeni descent, was a key figure in al-Qaeda in the Arabian Peninsula (AQAP).

He is believed to have been behind a number of attempts to attack the US.

Mr Obama said that as a leading AQAP figure, Awlaki had taken the lead in "planning and directing efforts to murder innocent Americans" and was also "directly responsible for the death of many Yemeni citizens".

He said Awlaki had directed attempts to blow up US planes and had "repeatedly called on individuals in the United States and around the globe to kill innocent men, women and children to advance a murderous agenda".

His death, said Mr Obama, "marks another significant milestone in the broader effort to defeat al-Qaeda and its affiliates".

The president also paid tribute to the work of both the US intelligence agencies and Yemeni security officials who had co-operated on the killing.

"This is further proof that al-Qaeda and its affiliates will find no safe haven anywhere in the world," he said, but warned that AQAP "remains a dangerous though weakened terrorist organisation".