The Foreign Ministry says three more foreign vessels allegedly entered South Korean ports with illegal North Korean coal shipments last year.

A ministry official said Thursday that the Korea Customs Service is probing the three ships, registered to Panama and Belize, over suspicions they brought in North Korean coal to the South in breach of UN sanctions.

The vessels allegedly brought in 15-thousand tons of North Korean coal to South Korea from Russia through the ports of Donghae and Pohang last November.  Korea South-East Power, a subsidiary of South Korea's state owned Korea Electric Power Corporation, is suspected of importing nine thousand tons of the shipment and the custom service is looking into the allegation. 

The customs service is also currently investigating the Panamanian-flagged Sky Angel and the Sierra Leonean-flagged Rich Glory, which both entered South Korea last year carrying roughly nine-thousand tons of North Korean coal.

Customs officials are considering whether or not to seize the ships in line with UN Security Council resolutions should they re-enter South Korea or pass through South Korean waters. 

The customs officials are also mulling taking legal action against South Korean businesses that imported the North Korean coal.