Unknown gunmen kidnapped two foreign nationals working with the international charity Doctors Without Borders (MSF) in Yemen's central province of Marib, a security official said on Tuesday.

The official said the abducted foreigners were identified as nationals from Germany and Myanmar, both serving under the MSF banner.

While acknowledging it has lost contact with its staff members in Yemen, MSF refrained from providing additional information, citing concerns for the safety of the abducted workers.

No group has claimed responsibility for the abduction so far.

Kidnappings of foreign aid workers and journalists have been a recurring issue in Yemen, which has been embroiled in a prolonged civil war between the Houthi rebels and the country's government forces since 2014.