A German nurse with the International Committee of the Red Cross (ICRC) has been kidnapped in Somalia's capital Mogadishu, the aid group says.
Armed men seized Sonja Nientiet from the ICRC compound at 20:00 local time (17:00 GMT) on Wednesday.
The 10 remaining international staff are being evacuated to Nairobi until further notice, the ICRC told the BBC.
A Somali woman working for the World Health Organization, also in Mogadishu, was shot dead by gunmen on Tuesday.
A relative of the woman, identified as Mariam Abdullahi Mohamed, said she was targeted while at a market buying items in preparation for her wedding next week.
There is no suggestion her killing and Ms Nientiet's abduction are linked.
Decades of conflict have made the country one of the world's most dangerous for aid workers, but security has improved in recent years and Wednesday's kidnapping is the first involving a foreign worker in almost 10 years.
It is however the second attack on ICRC staff in as many months - Somali employee, Yusuf Ibrahim, died on 25 March after an improvised bomb exploded under his car as he left the ICRC compound.
"We are deeply concerned about the safety of our colleague," said Daniel O'Malley, the ICRC's deputy head of delegation for Somalia, in a statement.
Ms Nientiet, who has worked for the ICRC since 2014 in conflict zones, arrived in Somalia in January. She had been delivering first aid training to local Somalis in the capital this week.
An ICRC spokeswoman told the BBC: "She is a nurse who spends her days caring for vulnerable people in Somalia - a true humanitarian."
Staff believe the kidnappers took their colleague out through a back door, avoiding security guards stationed at the main entrance of the ICRC compound, Reuters reported.
A government spokesman said they had identified one of the security guards of the compound as being involved in the kidnapping.
Witnesses told AFP news agency they saw a guard help the kidnappers put Ms Nientiet into a waiting vehicle with a punctured tyre.
Security forces later found an abandoned vehicle, which had broken down, believed to have been used in the abduction, officials said.
A police hunt for the nurse is under way. It is not known who is behind the kidnapping, but al Qaeda-linked al-Shabab militants are still active in the country, launching regular attacks.
The Swiss-based ICRC, which has provided humanitarian aid in Somalia for years, has temporarily suspended activities in Mogadishu but said Somali staff would continue ICRC's programmes outside the capital.
Somalia collapsed into anarchy in 1991 when war lords overthrew a military regime. Major armed conflict has since subsided, which allowed for parliamentary and presidential elections to take place in 2012.