A security official with the U.S. Embassy in Yemen was shot dead on his way to work Thursday, Yemeni officials said.
The killing of Qassim Aqlan, a Yemeni national, bears the hallmarks of al-Qaida, the officials said.
Al-Qaida in the Arabian Peninsula has been blamed for numerous attacks in Yemen.
Gunmen on a motorcycle shot at the vehicle Aqlan was in. He died at the scene, Interior Ministry officials said.
"Motorcycle attacks are currently al-Qaida's main tactic," a senior Interior Ministry official said, adding that such attacks "are easier for terrorists to coordinate and plan for."
The shooting took place along Siteen, a main street in the Yemeni capital of Sanaa, which is generally considered one of the safest, officials said. The Yemeni president's house is on the same road.
"We are deeply saddened by the killing," said U.S. State Department spokeswoman Victoria Nuland.
"We condemn this vicious act in the strongest terms possible and extend our deepest condolences to his family and friends at this difficult time."
Aklan was a foreign service national investigator for the embassy for the past 11 years, Nuland said in a statement. "He was a dedicated professional who will be greatly missed. We are coordinating closely with the Yemeni authorities to investigate this attack and to help bring those responsible to justice."
While some Interior Ministry officials at first said Aqlan was overseeing the investigation into an attack last month on the U.S. Embassy in Sanaa, others later told CNN he was not.
The U.S. State Department said he was not involved in the investigation.
Interior Minister Abdulkader Qahtan is overseeing that investigation, said a Yemeni government official not authorized to speak to the media.
Aqlan's death "sends a message that if you're working with the Americans you'll be targeted no matter who you are," the official said.
Hundreds of demonstrators gathered in front of the embassy in September to protest the video "Innocence of Muslims," which maligns the Prophet Mohammed. The demonstration turned violent, and some protesters broke into the embassy.
Clashes between security forces and demonstrators left at least four protesters dead and more than 30 people injured.