South Korean authorities were questioning on Monday six North Koreans rescued over the weekend as they drifted in the sea off the east coast and will send them home if they want to go, the South's Unification Ministry said.

The rescue comes as South Korea's new liberal government has pledged a more moderate approach to North Korea including engagement and reopening a communication channel that has been severed amid tension over its arms programmes.

The six are believed to have been on two fishing vessels, one of which was overturned, when they were rescued by the South Korean coast guard and the navy on Saturday, the coast guard said.

The six were being questioned by a South Korean team, and would be asked if they wished to be repatriated to the North, Unification Ministry spokesman Lee Duk-haeng told a briefing.

If so, they would be sent home, said the ministry, which handles ties with the North.

Such questioning by South Korean authorities is routine when North Koreans are rescued at sea.

The South returned eight North Koreans and their vessels in December after rescuing them off the east coast, in line with their wishes.

Lee said incidents such as the rescue and the repatriation of the crew were examples of why an open line of communication between the two Koreas was needed.

South Korea imposed unilateral sanctions against the North after its fourth nuclear test and a long-range rocket launch last year, in addition to sanctions applied in 2010 after the sinking of a South Korean navy ship that Seoul blamed on the North.

North Korea denied involvement in the sinking.

The sanctions cut off almost all exchange between the rival states that had been set up since 2000, when South Korea's "sunshine policy" brought a period of cautious rapprochement.