A North Korean shipping company slapped with U.N. sanctions after its freighter was seized last year for smuggling weapons from Cuba is operating as normal in Chinese waters, a website that monitors events in the North said Saturday, citing an analysis of shipping data.

The U.N. blacklisted the North Korean company, Ocean Maritime Management (OMM), about two months ago for operating the freighter, which was detained by Panamanian authorities in July last year while carrying Soviet-era MiG-21 fighter aircraft, surface-to-air missiles and other arms-related cargo hidden under sacks of sugar.

Under a U.N. Security Council resolution, all U.N. member states, including China, are required to freeze the North Korean firm's assets and enhance inspections of OMM-owned ships.

"But analysis of ship inspection records shows that the frequency of inspection on OMM linked ships has not increased, indicating that Chinese inspection authorities have not upped the scrutiny on the company's vessels despite recent resolutions," the website NK News said.

Out of 14 vessels operated by the North Korean firm, 10 ships have broadcast location data since June in Chinese waters, indicating that they are still operating in Chinese ports, it said.

One of the vessels operating in Chinese waters is the Chong Chon Gang, the ship seized by the Panamanian government, according to the website.   

In a traditional tactic to sidestep U.N. sanctions, the North Korean shipping firm appears to have also begun the process of renaming and re-assigning its vessels to other owners, it said.

Political ties between China and North Korea have appeared strained since Pyongyang apparently ignored Beijing and detonated its third nuclear device in February last year.

China has grown increasingly frustrated with North Korea's wayward behavior, but many analysts believe that Beijing will not suspend all economic support for Pyongyang out of fears it could precipitate the collapse of the regime in the impoverished country. (Yonhap)