The United Nations has imposed a global port ban on four vessels found violating sanctions against North Korea.

The four ships were found carrying coal, seafood and iron ore - exports banned by a UN resolution in August. The ban was expanded last month to include textiles and North Korean guest workers and also capped oil exports.

Hugh Griffiths, the coordinator of a UN Security Council panel on North Korea sanctions, said it was an unprecedented move. 

"There are four vessels that have been designated by the committee. The designation doesn't mean an assets freeze or travel ban. But it's a port ban," adding the ships were found "transporting prohibited goods."

"It's a pretty swift and decisive action by the committee," he added.

Mr Griffiths was speaking at the conclusion of a UN meeting open to all member states.

North Korean diplomats were present at the meeting but did not speak, according to diplomats.