Gunmen are on the run with two Spanish aid workers kidnapped yesterday from Kenya's Dadaab refugee camp.
It is the third abduction of westerners in Kenya by attackers linked to Somalia in a month.
Kenyan and Somali security forces were hunting for the kidnappers along the border between the two countries, which has been sealed off.
Police said they suspected Somalia's al-Qaeda-linked al-Shabaab insurgents were behind the kidnapping of the two women who work for Médecins Sans Frontières.
One of the two women has been named as Montserrat Serra i Ridao, a native of Gerona, northeast Spain, Spanish media reported, citing MSF and Spain foreign ministry sources.
The other aid worker is from Madrid, the reports said.
MSF had declined to disclose the identity of the two women at a news conference.
A senior al-Shabaab official, who did not want to be named, dismissed the claims.
"We heard about the MSF abductions but we were not behind it," the official in southern Somalia told Reuters by telephone.
"Nor have they been brought into any area under our control."
Al-Shabaab controls large parts of southern and central Somalia, including areas close to the border with Kenya.
The Spanish foreign ministry said in a statement that it is in contact with the families of the kidnapped aid workers and it is "doing everything it can to free the two women".
A local Kenyan intelligence source said security forces were investigating reports a man had stumbled across the women's vehicle, abandoned between Dadaab and the frontier.
Somali politician Abdi Bule Hussein, from the Lower Juba border area, said he too had heard the vehicle had been ditched.
"We strongly condemn this attack", Jos Antonio Bastos, the president of MSF Spain, said in a statement.
"MSF is in contact with all the relevant authorities and is doing all it can to ensure the swift and safe return of our colleagues.”
A spokesman at the Spanish Foreign Ministry confirmed the missing women were Spanish.
Aid workers have been targeted for abductions on numerous occasions in Somalia, where kidnappings can be a lucrative business, but attacks in Kenya had been relatively rare.
