Two South Koreans have been released unharmed after being abducted by an unidentified armed group in southern Nigeria, Seoul's foreign ministry said Saturday.

The two men in their 50s and 60s, respectively, were taken during an ambush by the group in Gbaran in the southern district of Enwe in the West African country on Dec. 12, according to sources. They are employees of Daewoo Engineering & Construction Co., a major South Korean builder.

South Korean authorities secured the custody of the two on Friday, local time, and both of them remain in good shape, the ministry said in a text message sent to reporters.

"They are in a safe place and have talked to their families," the ministry said.

Four Nigerian security personnel and two drivers were killed during the ambush while a third driver managed to escape from the scene despite suffering an injury. They were all Nigerians.

In a press release, Daewoo said both employees are in "good health" and will undergo local procedures and return to Korea as soon as possible.

"We thank the governments of the Republic of Korea and Nigeria for their generous support by mobilizing all diplomatic channels to secure the safe release of the kidnapped employees," the company said.

Seoul officials assumed that the latest abduction took place for ransom rather than for terrorist motives, as most of terrorist groups in Nigeria are based in the northern part of the country, according to sources.

Abductions for ransom are common in parts of Nigeria with cases totaling some 800 this year and 1,129 cases last year.

Some 405 South Koreans are currently in Nigeria. Of them, about 340 people are employees of major South Korean companies, including Daewoo, Samsung, Hyundai and Lotte.

South Korean workers were the target of kidnappings in Nigeria in the past, with one case in 2006, two cases in 2009 and two others in 2012. They were all released either on ransom or after accepting the kidnappers' demands. (Yonhap)