SEOUL  -- The Republic of Korea (ROK) plans to impose its unilateral maritime sanctions against the Democratic People's Republic of Korea (DPRK) by banning third-country ships visiting the DPRK from entering ports of the ROK, Yonhap news agency reported Friday citing the maritime ministry.

The Ministry of Oceans and Fisheries was quoted as saying that the maritime restrictions against the DPRK would be implemented "immediately" after decision by the national security council (NSC) under the presidential office Cheong Wa Dae.

Restrictions on third-country ships would be an expansion from the May 24 sanctions, imposed by Seoul after the sinking in March 2010 of a warship that killed 46 sailors.

The ROK has blamed the sinking on a DPRK torpedo attack, while Pyongyang has denied any involvement.

Under the May 24 sanctions, DPRK ships are banned from entering ports of the ROK and sailing past territorial waters of the ROK.

Japan prohibited DPRK ships and third-country vessels visiting the DPRK from entering Japanese ports as part of its unilateral sanctions against the DPRK's recent rocket launch and nuclear test.