“We are deeply concerned about the safety of our colleague,” said Daniel O'Malley, ICRC's deputy Somalia head.
“She is a nurse who was working every day to save lives and improve the health of some of Somalia's most vulnerable people.”
The Red Cross said the attack happened around 8.00 pm local time when unidentified armed men entered its compound in Mogadishu, adding it is “in contact with various authorities to try and secure her release”.
People working for the Red Cross in Somalia told AFP the gunmen appeared to have evaded the compound's security guards and snuck the nurse out through a back entrance and into a waiting vehicle.
A government security officer said investigations were underway. “We have received information indicating a female western staff member was kidnapped from the ICRC office in Mogadishu,” said Abdirahman Mohamed.
Somalia, which collapsed into civil war in 1991 and has been the site of an al-Qaeda-linked Islamist insurgency since 2006, is one of the most dangerous countries for aid workers, but abductions remain relatively unusual.
In the past, foreigners, including journalists and aid workers, have been kidnapped by armed gangs or Shabaab militants and held for ransom, sometimes for years at a time.
Terrorist bombings and assassinations are commonplace and frequently claimed by the Shabaab which is fighting to overthrow the internationally backed government in Mogadishu.
International aid agencies, including the independent Switzerland-based ICRC, provide health care and other basic services in the war-torn country and are regarded as supporters of the government by the Shabaab and as a ready source of income by other militants and armed gangs.
On Tuesday a local employee of the World Health Organization (WHO) was shot in Mogadishu.
The WHO said in a statement Wednesday it was “shocked and saddened” by the killing of Mariam Abdullahi Mohamed, “a dedicated frontline worker”.
Between 2008-12 piracy off the coast of Somalia became a big business with crew-members and their ships held for million-dollar ransoms, but in recent years attacks have become rare.
Gradually improving stability in Somalia allowed the holding of limited elections in 2016, but insecurity remains widespread.
In October, Somalia suffered its deadliest-ever bombing, with over 500 people killed in an attack blamed on the Shabaab.