News reports that Chinese and Russian companies were involved in ship-to-ship transfers of oil and oil products to North Korean ships at sea raises concern about the effectiveness of UN sanctions.

Beijing and Moscow deny breaking UN sanctions, but it seems difficult for them to escape suspicions of connivance. They must take note of the consequences of loopholes in sanctions and must implement them more actively and responsibly.

Japan’s Yomiuri Shimbun daily on Monday revealed transaction documents showing Chinese and Russian trading companies’ illicit sales of petroleum products to North Korea.

South Korea last month reportedly seized a Panama-flagged oil tanker suspected of transferring oil products to North Korea at sea in breach of UN sanctions. The tanker, named KOTI, was detained at Pyeongtaek-Dangjin and its crew are being investigated. The KOTI came to the South Korean port in December from Shidao Port, Shandong province, China.

South Korea is also holding the Lighthouse Winmore, a Hong Kong-flagged tanker, and its crew members for allegedly violating UN sanctions by transferring oil to a North Korean vessel in October.

The UN Security Council on Dec. 22 imposed new sanctions on North Korea that allow member states to seize, inspect and freeze vessels suspected of transferring banned goods to or from North Korea.

Beijing plays innocent, saying it has nothing to do with the Lighthouse Winmore, as the vessel was chartered by the Billions Bunker Group, a Taiwanese company. But the ship is registered in Hong Kong and Lighthouse Shipping Development, the shipping company that manages the seized tanker, registered its address in Guangzhou, China. Of the 25 crew members, 23 are Chinese, including the captain. Lighthouse Shipping Development’s denial of knowledge of the tanker being used for trade with North Korea is less than convincing.

Reuters reported Saturday that Russian tankers have supplied fuel to North Korea on at least three occasions in recent months by transferring cargo at sea. This is a different case from that in the Yomiuri report.

Russia’s Foreign Ministry has denied breaking UN sanctions against North Korea. It noted that related resolutions imposed limits on North Korea’s refined oil imports rather than banning them altogether.

But some of the Russian vessels made unusual movements.

The Russian-flagged tanker Vityaz left the port of Slavyanka near Vladivostok in Russia on Oct. 15 with 1,600 tons of oil. The ship’s agent claimed its destination as the sea west of Japan, but the vessel switched off its transponder as it sailed into open waters.

The Vityaz is believed to have conducted a ship-to-ship transfer with the North Korean-flagged Sam Ma 2 tanker in open seas.

Two other Russian-flagged tankers made similar journeys between the middle of October and November.

There is no evidence that illicit trade with North Korea is backed by the Chinese or Russian states. But circumstances point otherwise. Their connivance or abetting comes under reasonable suspicion. Beijing and Russia claim officially that they have been strictly implementing the UN Security Council sanctions, but they are reputed for being passive to the sanctions.

North Korea is said to have acquired materials and equipment needed for its nuclear and missile programs from Chinese trading companies. Contraband trade with the North explains why it has been able to conduct nuclear and missile tests continuously despite tightening sanctions. If China had ceased oil supply to North Korea early, its nuclear and missile program may not have come to its current stage.

Now the likelihood of a military clash on the Korean Peninsula is higher than ever. China and Russia have a lot to answer for in an aggravated security situation on the peninsula. If they keep playing innocent, they will face a nuclear state ruled by a wayward dictator or a military clash no one wants.

The international community must try harder to find loopholes in its sanctions and close them. As long as there are loopholes, any efforts to resolve the North Korean nuclear problem will be useless.