SANAA (AFP) - US-born cleric Anwar al-Awlaqi, a prominent Al-Qaeda chief described by US officials as 'the most significant risk to the United States, was killed on Friday in what analysts called a 'significant blow. A senior US official confirmed Awlaqis death after an announcement by the Yemeni defence ministry. I can confirm... hes dead, the senior administration official said, without providing further details. In Sanaa, the defence ministry said Awlaqi was killed on Friday morning but did not elaborate on the circumstances of his death. Tribal sources told AFP that Awlaqi, who was on a US wanted list, was killed in an airstrike on two vehicles in Marib province, an Al-Qaeda stronghold in eastern Yemen, early in the day. One of them quoted what he said was a man travelling behind Awlaqi in a second vehicle and who was himself wounded. The man, Khamis Arfaj, said Awlaki and two others, one of them Arfajs brother, Salem, were killed instantly from a direct missile hit to their pick-up truck. The source said he suspected they died in an American drone strike, saying US planes have been flying overhead for days now. Then this morning, at about 9:30, what appeared to be a US aircraft fired on the two cars Awlaqi and his fellow operatives are believed to have been travelling in, he said. US Republican Representative Peter King, chairman of the House Committee on Homeland Security, called Awlaqis killing a great success in our fight against Al-Qaeda and its affiliates. For the past several years, Al-Awlaqi has been more dangerous even than Osama bin Laden had been. The killing of Awlaqi is a tremendous tribute to President (Barack) Obama and the men and women of our intelligence community, he said. Al-Qaeda leader bin Laden was killed when US special forces raided his compound in Abbottabad on May 2. Another tribal source, also on the condition that he not be identified, spoke of rumours that Awlaqi had recently changed locations within Yemen. Up until three weeks ago, he had been believed to be hiding out in the southern Shabwa province, another militant bastion. But then word came that Awlaqi was in fact in Marib province, a move he made sometime in the last three weeks, the source said. The source added that Yemeni security forces have been more actively seeking Awlaqi in Marib since the speculation that he had moved. He said Awlaqi, feeling threatened by the boosted efforts to capture him, fled Marib last week to hide out in the nearby al-Jawf province on the Saudi-Yemeni border. A US-based group specialised in monitoring militant organisations described Awlaqis death as a significant blow to Al-Qaeda in the Arabian Peninsula . IntelCenter said in a statement that Awlaqis death would especially impact the groups ability to recruit, inspire and raise funds. It said that although AQAP would suffer because of Awlaqis 'unprecedented ability to 'influence and connect to a broad demographic of potential supporters, it remains one of the most dangerous militant branches in the region. Earlier this month, the Washington Post had said that the United States was building an array of secret new drone bases to conduct strikes against Al-Qaeda targets in both Yemen and Somalia. Yemeni authorities officially deny the use of drones against Al-Qaeda targets in their country, saying Washington provides only logistical support to Sanaas fight against extremists. Witnesses and residents of the southern province of Abyan, where the government is fighting an ongoing battle against Al-Qaeda-linked militants, regularly charge that American drones are carrying out airstrikes there. IntelCenter said that despite Awlaqis death, AQAP still posed a direct threat to the US, adding that the groups leader, Nasir al-Wuhayshi, who is blamed for planning attacks on American territory, remains in charge. In February, the US director of the National Counterterrorism Centre, Michael Leiter, told lawmakers Awlaqi probably posed the most significant risk to the United States. Awlaqi, a US-Yemeni citizen who had eluded capture for years, was believed to be a key AQAP leader. The charismatic preacher who spoke fluent English was seen as having the unique ability to recruit Al-Qaeda operatives in the West. In April last year, a US official said the Obama administration had authorised the targeted killing of Awlaqi, after American intelligence agencies concluded the cleric was directly involved in anti-US plots. US intelligence officials believe Awlaqi was linked to a US army major who allegedly shot dead 13 people in Fort Hood, Texas, and to a Nigerian student accused of trying to blow up a US airliner on December 25, 2009.