MOGADISHU, Somalia  Four aid workers were kidnapped in the southwestern Somali town of Wajid on Monday, officials said, the latest in a series of attacks against humanitarian workers in this anarchic nation.

The four  three foreigners and a Somali  were hijacked by unidentified militias on their way to the Wajid airstrip early Monday morning to catch a flight to Nairobi, Kenya, a United Nations employee in Wajid said in a telephone interview on the condition of anonymity. United Nations officials in Nairobi later released a statement confirming the abductions but offering no additional details.

The identity of the three foreigners was not immediately known, and no group claimed responsibility.

Somalia is one of the most dangerous countries in the world for foreigners, who become prime kidnapping targets for gunmen seeking ransoms of millions of dollars. Dozen of foreigners, including journalists and aid workers, have been abducted since last year. Some have been held for months, like two journalists seized last August. Much like the pirates who hold ships and crews for ransoms off Somalia’s eastern coast, the kidnappers generally release the foreigners unharmed once ransoms are paid.