Seoul - Former US president Bill Clinton asked North Korean leader Kim Jong Il to free South Korean detainees during his talks in Pyongyang, but there was no information on the Norht's response, South Korean ministries said Thursday.

North Korea is holding four fishermen for allegedly violating its territorial waters and a manager from an industrial park accused of criticizing the regime.

Clinton appealed for the release of the South Koreans on humanitarian grounds, said South Korean Foreign Ministry spokesman Moon Tae Young.

"I've heard this information from the US State Department official in its letter of appreciation for our support of Clinton's visit to Pyongyang," the spokesman said.

The spokesman added that there was no information on Kim's response to Clinton's appeal.

North Korea remained silent Thursday on Seoul's plea to free its citizens, the South Korean Unification Ministry said Thursday.

The silence on the detained South Koreans contrasts with the high-profile release of two US journalists who flew back to be reunited with their families in the US after facing a 12-year-sentence of hard labour for illegally crossing the North Korean border.

The North has denied access to a South Korean manager since he was detained on March 30 at the jointly-operated industrial park of Kaesong for allegedly criticizing the North Korean regime.

North Korea said Saturday the South Korean squid fishing boat with four crew members aboard "illegally intruded" into its territorial waters, an incident that South Korea said was accidental. (dpa)