Britain has effectively deported two London-based officials of North Korea's state insurance firm by refusing to renew their visas after the firm was slapped with sanctions in the wake of Pyongyang's January nuclear test, a diplomatic source said.

In April, Britain blacklisted the North's Korea National Insurance Corp. and its London office in line with European Union sanctions imposed after the North's fourth nuclear test in January and a long-range rocket launch in February.

"It's part of implementation of sanctions to deny visas for those working for a sanctioned entity," a source said.

The EU said in April that the North's firm is "generating substantial foreign exchange revenue which could contribute to the DPRK's nuclear-related, ballistic-missile-related or other weapons-of-mass-destruction-related programs."

The EU also said that the firm's headquarters in Pyongyang is linked to "Office 39" of the North's ruling Workers' Party, which takes care of secret funds of the communist regime.

The North's firm has also been blacklisted by the U.N. Security Council. (Yonhap)