REPUBLIKA.CO.ID, SEOUL -- Malta has denied visa extensions for North Korean workers, effectively expelling them, due to a diplomatic campaign by South Korea and human rights groups, South Korea's Yonhap news agency reported on Thursday.

South Korea has been pressing the few countries that have ties with North Korea to push for changes in the isolated state, which has been criticised for its human rights record and for channelling wages earned by its workers abroad back to the North.

Malta has denied visa extensions for about 20 North Korean workers who had been employed at a construction firm and a clothing maker there, Yonhap reported, quoting unidentified sources in the Malta government and the companies.

All of the workers had since left Malta and returned to North Korea, Yonhap reported.