Motorcycle-riding gunmen linked to Al Qaeda shot and killed an American teacher in the Yemeni city of Taiz on Sunday, and Yemeni officials said government forces killed up to 14 militants in clashes and artillery attacks on their strongholds.
The attacks underscore the challenges facing President Abd-Rabbu Mansour Hadi who took office last month after a year of massive protests against his predecessor Ali Abdullah Saleh.
A police source in Taiz said a gunman riding on the motorcycle driven by an accomplice shot a US English language teacher who was also deputy director of a language school, the Swedish Institute.
Officials from the institute identified the victim as Joel Shrun and said he was born in 1983.
The gunmen, who escaped after the attack, were believed to be linked to Al Qaeda, the police source said. A group affiliated with the militant network claimed responsibility.
"This operation comes as a response to the campaign of Christian proselytizing that the West has launched against Muslims," an unidentified person said in a text message to journalists, claiming responsibility on behalf of the Al Qaeda-linked Ansar al-Sharia (Partisans of Islamic Law).
Islamic militants often accuse Western aid groups of proselytising.
Al Qaeda violence on rise
Yemen has seen an escalation of Al Qaeda violence since Hadi took office in February vowing to fight the Islamist network.
Taiz, 120 miles south of Sanaa, is a commercial hub where many foreigners live and work. It was a flashpoint for protests against former President Ali Abdullah Saleh's 33-year rule.
Also on Sunday, a government warplane bombed Islamist militants in the southern city of Jaar, causing people to flee their homes, residents said. There were no immediate reports of casualties.
Ansar al-Sharia captured Jaar in Abyan Province in March last year after the outbreak of protests against Saleh and have turned it into their main base in southern Yemen.
Daily clashes break out around areas controlled by militants in southern Yemen. A local official said that up to 14 militants were killed in artillery attacks and clashes on Saturday north of the Abyan provincial capital of Zinjibar, the area of Bagdar and the town of Jaar.
The United States and Saudi Arabia, Yemen's neighbor and the world's biggest oil exporter, are concerned about Al Qaeda's expansion in Yemen where it has regrouped after suffering reverses in Iraq and Saudi Arabia.
In early March, militants killed more than 110 soldiers in twin suicide attacks and said they had also captured some 70 soldiers.
* Additional reporting by Mohammed Mukhashaf in Aden; Writing by Sami Aboudi and Martina Fuchs; Editing by Robin Pomeroy.