Anwar al-Awlaki: Senior Al-Qa'ida activist who was linked to terrorist atrocities including the attacks of 9/11

The radical US-born cleric Anwar al-Awlaki, who was killed in Yemen yesterday, was one of al-Qa'ida's most dangerous figures in their global terrorist network.

He was believed to have been linked to a series of attacks including 9/11, the shootings at Fort Hood in 2009 and the failed Christmas Day "underwear bomber" the same year.

Al-Awlaki, who had dual US-Yemeni citizenship, was killed yesterday morning five outside Kashef in the al-Jawf Province, 90 miles east of Sanaa, the capital, in what is believed to have been a manned air strike, although a drone attack has not been ruled out. Local tribal officials said that a two-car al-Qa'ida convoy had been targeted and destroyed.

His death is the most significant setback to the al-Qa'ida organisation since Osama bin Laden's assassination in May. Al-Awlaki was one of the few senior operatives schooled and orientated to western behaviour with an understanding of the western psyche. In recent years he had gone from mild criticism of his country to increasing vociferousness in his calls for Muslims to wage jihad against the US, propelling him towards the top of the Americans' "kill or capture" list and making him a target for assassination by US forces or CIA drones. His death is certain to deprive al-Qa'ida of one of its most powerful propaganda tools.

This designation as "one of the most dangerous men alive", as the UN Security Council referred to him, was a recognition that al-Awlaki had risen in the ranks of anti-Western Islamic extremism. His provocative rhetoric had become renowned on jihadi websites. With all the paraphernalia of an educated modern-day terrorist, al-Awlaki was able to strike anywhere in the world using online resources – not for nothing was he known as "the bin Laden of the internet". He ran a blog, had a Facebook page and had posted hundreds of videos of his sermons on YouTube, where he gained a wide audience of disenchanted Western Muslims who might otherwise have been beyond al Qa'ida's reach.

He was believed to have been the leader of al-Qa'ida foreign operations unit inside the Arabian Peninsula group, which has in recent years taken centre stage in the global campaign of jihad inspired by Bin Laden. US officials suggested that he could emerge as bin Laden's successor.

The son of a future Yemeni Agriculture Minister and university president, Anwar Nasser Abdullah Al-Awlaki was born in Las Cruces, New Mexico in 1971. His father, Nasser, was studying agricultural economics and the family lived in the US for another seven years before returning to Yemen. After studying Islam during his teenage years, al-Awlaki returned to the US in 1991, gaining a BSc in civil engineering from Colorado State University and a master's in education from San Diego State.

In 1994, al-Awlaki married a cousin from Yemen and took a part-time job as imam at the Denver Islamic Society. He later became imam at a mosque in Fort Collins, Colorado, before returning to San Diego in 1996, where he took charge of the city's Masjid Ar-Ribat al-Islami mosque. During his four years there, his sermons were attended by at least two of the 9/11 hijackers, both of whom were also seen attending long meetings with the cleric.

In early 2001, he moved to the Dar al-Hijrah mosque in Falls Church, Virginia, which was attended by a third hijacker. It later emerged that in 1998 and 1999, while serving as vice-president of an Islamic charity that the FBI described as "a front organisation to funnel money to terrorists", al-Awlaki was visited by Ziyad Khaleel, an al-Qaida operative, and an associate of Sheikh Omar Rahman, who was serving a life sentence for plotting to blow-up landmarks in New York.

In 2002, al-Awlaki left the US for the UK, where he gave a series of popular lectures to Muslim youths. However, unable to support himself, he returned to Yemen in early 2004 and lived in his ancestral village in the southern province of Shabwa with his wife, whom he married in 1994, and their children. He became a lecturer at al-Iman University, a Sunni religious school in Sanaa headed by Abdul-Majid al-Zindani, a cleric who was later designated a terrorist by the US and UN for his suspected links with al-Qaida.

In August 2006, al-Awlaki was detained by the Yemeni authorities, reportedly on charges relating to a plot to kidnap a US military attaché; he was jailed for 18 months. Following his release he became more overtly supportive of violence, railing against the US-led invasions of Afghanistan and Iraq and the killing of Muslims in covert operations in Pakistan and Yemen. He incited violence in a number of texts via his online communications and many pamphlets and CDs, including one entitled 44 Ways to Support Jihad; such material was found in the possession of several convicted English-speaking militants in Canada, the UK and US.

With recent attacks and attempted attacks on US soil, after investigation, al-Awlaki was soon credited with inspiring or directing a number ofplots – the shooting of 13 people inside the Fort Hood military base in Texas, the failed Christmas Day underwear bomber, the failed Times Square bombing and a plot in which two parcel bombs were hidden inside printer cartridges on US-bound planes (they were intercepted in the UK and Dubai).

His influence was also seen in plots to target British and European interests. In 2010, inspired by his sermons, Roshonara Choudhry was found guilty of the attempted murder of the MP Stephen Timms, who had voted for the invasion of Iraq, while a British Airways employee, Rajib Karim, was convicted in February 2011 of plotting attacks against the airline.

In November 2009, the Yemeni authorities put al-Awlaki on trial in absentia, charged with inciting violence against foreigners in connection with the murder the previous month of a French security guard at an oil company's compound. He went into hiding. In March and November 2010, al-Awlaki intensified his rhetoric with two videos; the first called for Muslims residing in the US to attack their country of residence, while the second called for the killing of Americans, claiming they were from the "party of devils". Weeks later, he survived an air strike in Shabwa province in which at least 30 militants were killed.

Anwar Nasser Abdullah al-Awlaki, lecturer, imam and Al-Qa'ida activist: born Las Cruces, New Mexico 22 April 1971; married 1994 (children); died Mar'rib, Yemen 30 September 2011.