Gunmen on motorbikes kill man believed to have been a language teacher in southern city of Taiz, officials say.

Ansar al-Sharia claimed the American teacher had been spreading Christianity [EPA]

Two gunmen have killed a US citizen in southwestern Yemen in an attack that was claimed by an armed group associated with al-Qaeda.

The assailants, who were riding a motorbike, shot the man in his car while he was driving in Taiz, then fled the scene, a Yemeni official told the AFP news agency.

The man was believed to have been a teacher working at the International Training and Development Centre in the southern city. The US state department confirmed that a US citizen had been killed but did not give any other details.

Ansar al-Sharia, an armed group linked to al-Qaeda, claimed responsibility for the attack in a text message circulated among local media. The group claimed the man had been a Christian missionary and that they attacked him to respond to “a Western campaign to preach Christianity among Muslims”.

Witnesses said that the attackers were dressed in the uniform of the elite Republican Guard, which is led by the son of former Yemeni president Ali Abdullah Saleh.

Al-Qaeda in the Arabian Peninsula, the extremist group’s franchise in Yemen, is active in the south and east but not in Taiz, which was a major centre for the opposition movement that eventually forced former president Saleh to step down.

Hardline Muslim fighters have exploited the weakening central government in Sanaa to strengthen their presence in parts of the country that are not under tight government control.

The attack comes two days after suspected al-Qaeda gunmen abducted a Swiss woman, also a teacher at a language school, in the Red Sea port of Hodeida and moved her to the restive Shabwa province further east.

Meanwhile, a warplane bombed suspected extremist groups in southern city of Jaar, causing the population to flee their homes, residents said, but there were no immediate reports of people killed or injured.

Armed groups captured Jaar in the Abyan province in March last year after the outbreak of protests against Saleh’s 33-year rule and have turned it into their main base in southern Yemen.

The raid comes after a spate of attacks by Ansar al-Sharia (Partisans of Islamic Law), the deadliest of which killed at least 110 conscripts last week, in a reminder of the challenges faced by newly elected President Abd-Rabbu Mansour Hadi.