A London-based web designer who is accused of training for terrorism and working as a propagandist for al-Qaida is facing a possible life sentence in a US prison after being extradited to New York, prosecutors announced on Tuesday.

Minh Quang Pham is charged with possessing and using an AK-47 rifle “in furtherance of crimes of violence”, receiving military-style training and providing support to al-Qaida in the Arabian Peninsula (AQAP), the Yemen-based branch of the terrorist network.

Pham, a 32-year-old Vietnamese citizen, boasted that he had “travelled to Yemen in order to join AQAP, and to wage jihad on behalf of AQAP”, according to US authorities in New York.

He is also accused of helping to produce Inspire, al-Qaida’s English-language magazine. Prosecutors have said the alleged 2013 Boston Marathon bombers may have learned how to construct explosives from the publication.

Announcing the charges on Tuesday, Preet Bharara, the Manhattan US attorney, said Pham’s support for al-Qaida began after he “surreptitiously travelled from the UK to Yemen in late 2010”, telling his wife in New Cross, south-east London, that he was going to Ireland.

“During the half year he spent in Yemen, Pham allegedly vowed to wage jihad, swore bayat (loyalty), and provided material support to high-level AQAP members, almost always brandishing a Kalashnikov rifle,” Bharara said in a statement.

Pham was previously reported to have converted to Islam after moving to the UK as a boy. He reportedly established a website and leaflet design company registered to his home in New Cross, where he had lived since 2005.

He is said to have been known as “Amin” to al-Qaida operatives. Prosecutors claim that he cooperated with two now-dead American members of al-Qaida. The men were not named by prosecutors but their descriptions appear to match those of Anwar al-Awlaki, the notorious New Mexico-born radical cleric, and Inspire’s editor, Samir Khan.

Prosecutors allege someone who later became a cooperating witness spoke to both men and “understood from them that Pham was providing valuable assistance” to the American who appears to be al-Awlaki “in connection with the production and editing of Inspire magazine”.

Al-Awlaki and Khan were both reportedly killed following an air strike in Yemen by a US drone in September 2011.

Pham is also alleged to have told the informant that he had travelled to Yemen intending to join AQAP for jihad, that he had sworn an oath of loyalty to an al-Qaida commander, and that he had spent time at three AQAP safehouses.

The 32-year-old was detained at Heathrow airport when he returned to the UK in July 2011, according to prosecutors, and was “found to be in possession of a live round of .762 caliber armor-piercing ammunition, which is consistent with ammunition that is used in a Kalashnikov assault rifle”. He was also allegedly carrying computer files identical to those possessed by the man who later became a US government witness.

Pham was arrested in the UK in June 2012 following an indictment issued in New York, prosecutors said, but had been challenging his extradition until a judge ruled against him and ordered his deportation last month. He arrived in the US last week and is due to be arraigned in court on Wednesday.

He is charged with five counts: conspiracy to provide material support to AQAP, providing material support to AQAP, conspiracy to receive military-type training from AQAP, receiving military-type training from AQAP, and the “use, carrying and possession of a firearm (machine gun) in furtherance of crimes of violence”. If convicted on all counts, he faces a maximum sentence of life in prison, and would be made to serve a minimum of 40 years.