Five South Koreans were abducted in a Mexican border city, officials said Tuesday.

Gunmen who seized the four men and one woman demanded a $30,000 ransom in return for their freedom, according to an official from the National Intelligence Service. The official did not give further details and asked not to be named, citing an internal policy.

South Korean President Lee Myung-bak instructed his top security adviser to "make utmost efforts for quick and safe return" of the kidnapped victims.

South Korea's Foreign Ministry said in a statement that the five were kidnapped in the Mexico border city of Reynosa last Monday when they were traveling there to seek job information. The ministry said the five were confirmed to be alive.

Mexico has a large South Korean population, many of whom are active in the import industry and own assembly-for-export factories.

Reynosa police officer Mario Gomez said local authorities were investigating the reports, but could not release any information.

Kidnappings for ransom have become commonplace in Mexico, which has one of the highest kidnapping rates in the world. Many are never reported to police, in part because of the fear that local officials may be involved or will bungle a possible rescue.

In October, Spanish businessman Jose Maria Sanchez was kidnapped, prompting international media coverage and intense pressure from the Spanish and U.S. governments. Three days after he was taken from a seaside restaurant, Sanchez was found wandering along a highway outside Tijuana, his hands still bound and his eyes blindfolded.