Gunmen kidnapped three Latvian helicopter crew members working for the World Food Programme in the troubled Sudanese state of South Darfur, a hotspot for abductions, the UN agency said on Friday.
The WFP said the three Latvians, whose air services were contracted to the agency for humanitarian operations, were abducted in the state capital of Nyala on Thursday.
In Riga, the foreign ministry said it was coordinating in efforts to secure the release of the three Latvians.
"We are working closely with Latvia's appropriate institutions and our foreign partners to find out more detailed information on how we can resolve that problem," foreign ministry spokesman Janis Silis told AFP.
Abdel Hamid Kasha, the governor of South Darfur, had previously said the three were Russians.
"Last night, unidentified gunmen stormed the home of three Russian pilots working for a private company that has a contract with the WFP and took them to an unknown location," he said.
"The security services searched for the kidnappers until nightfall" without success, said the governor.
The three kidnapped crewmen are employees of Latvian company GM Helicopters, said the Russian consul in Khartoum, Yevgeny Arzhantsev, quoted by Russia's ITAR-TASS news agency. "There are no Russians among the hostages."
UN sources said the crew was made up of two pilots and a mechanic.
The kidnapping came as Valerie Amos, the UN under secretary general for humanitarian affairs and emergency relief coordinator, began a five-day visit to Sudan that is scheduled to include Nyala.
"It is still my intention to visit Nyala. Of course I am extremely concerned about the kidnappings of UN colleagues," Amos said as her delegation visited southern Sudan.
"It is important that there is no culture of impunity that develops. Since 2009 and now we have 30 workers to have been kidnapped this is extremely serious."
Darfur has seen a wave of kidnappings for ransom since March 2009, when the International Criminal Court indicted Sudanese President Omar al-Bashir for alleged war crimes in the strife-torn western region.
The latest comes after a Hungarian civilian worker for the joint UN-African Union peacekeeping force in Darfur (UNAMID) was seized at gunpoint from his home in the Darfur city of El-Fasher in early October.
In August, an armed group abducted two Russian pilots from Nyala and two Jordanian police advisers deployed with UNAMID were kidnapped at gunpoint.
Thirty people including 26 foreigners have been kidnapped in the war-torn region since March 2009, with all the hostages released unharmed a few days later, except for the Hungarian and now the three Latvians.
Darfur has been gripped by a civil war since 2003 that has killed 300,000 people and displaced another 2.7 million, according to UN figures. Khartoum says 10,000 people have died in the conflict.