A Russian military expert was killed and another injured Tuesday when gunmen driving a motorbike opened fire on them in the Yemeni capital, Sana'a, local media reported.
The two were advisers to the Yemeni armed forces, the Barakish news website reported.
Drive-by shootings and abductions have increased since the 2011 uprising against longtime leader Ali Abdullah Saleh, who stepped down in 2012. Last week, a lawmaker was assassinated by assailants on a motorbike in Sana'a, dpa reported.
Authorities have blamed the violence on militants linked to al-Qaeda.
On Monday evening, 12 suspected members of al-Qaeda were killed in an air raid on the restive southern province of Abyan, according to a website affiliated with the Defence Ministry.
Authorities were trying to identify the bodies, it said.
Yemen is a stronghold of al-Qaeda in the Arabian Peninsula, and US drone strikes aimed at Islamist militants in Yemen have increased in recent month.
Militants have repeatedly called for attacks on foreign diplomats and embassies.