Authorities identified the victim as Joel Sharm and said two men riding a motorcycle fired eight shots at him as he traveled to his job at a Swedish language center in Taiz, CNN said. Al-Qaida in the Arabian Peninsula -- the terror group's affiliate in Yemen -- called Sharm one of the biggest missionaries in the country in a text message sent to media outlets, and said he was spreading Christianity to the Yemeni people.
"We are investigating the killing as this is the first of its kind against a Western national in Taiz," unnamed defense officials told the American broadcaster.
The U.S. Embassy has not confirmed that an American has been killed in the country, though it is investigating the reports, CNN said.
Taiz, located 173 miles from the country's capital Sana, has been a major center of opposition to former President Ali Abdullah Saleh, who stepped down last year after a 33-year rule.