Images taken from a Japanese spy plane show the North Korean-flagged Rye Song Gang 1 anchored next to another vessel early Tuesday morning, about 250 kilometers (155 miles) east of Shanghai. The Rye Song Gang 1 is one of eight ships banned from entering ports across the globe under UN sanctions targeting North Korea.
Japan's Ministries of Defense and Foreign Affairs said in statements the government "strongly suspects" the two ships were involving in the transferring of goods while at sea.
A United Nations Security Council resolution passed in September bans UN member states from facilitating or engaging in ship-to-ship transfers with North Korean-flagged vessels.
The other ship allegedly involved, the Wan Heng 11, flies the flag of Belize, but is owned and managed by a Hong Kong-based company, according to records from Equasis, a shipping information database developed by European Union and French authorities. Ship owners and managers often register their vessels in other places to avoid domestic regulations.
When asked about the images, Hugh Griffiths, the coordinator for the UN Panel of experts on North Korea -- which is charged with monitoring and reporting on sanctions enforcement -- told CNN, "I can confirm that the panel has received some information from Japan on this case, but unfortunately I cannot comment any further as this is currently the subject of an ongoing panel investigation."
This is the third time in recent months the Rye Song Gang 1 has been caught engaging in alleged ship-to-ship transfers at sea.
, the Japanese Ministry of Foreign Affairs released images showing the vessel engaging in another suspected ship-to-ship transfer. That follows the release of similar images by the US Treasury Department on October 19
, showing the Rye Song Gang 1 allegedly conducting an illicit transfer while in international waters.
Though the department did not name the other ship involved, the South Korean Foreign Ministry has since revealed it seized a Hong Kong-registered vessel, the Lighthouse Winmore, for transferring refined oil to a North Korean ship that same day.
Trading goods at port is significantly easier than at sea. North Korea's apparent reliance on ship-to-ship transfer is an indicator that sanctions have at the very least made it harder for the North's fleet to engage in open business. But the fact that the Rye Song Gang 1 has been continually caught violating international law, in international waters, also highlights flaws in sanctions enforcement.
"This is North Korea adapting and the only way that sanctions will work if those imposing the sanctions also adapt," said Anthony Ruggiero, an expert in the use of targeted financial measures at the Foundation for the Defense of Democracies.
The United Nations passed successive rounds of sanctions against the North Korean regime last year, targeting energy imports, coal exports and foreign labor and shipping, among other things.
The measures already passed against the North's shipping sector are considered a vital part of the Washington-led global pressure campaign targeting the North's leader Kim Jong Un and his regime.
The White House hopes sanctions will slow the development of the country's missile and nuclear programs, and strangle Pyongyang's economy to the point where Kim would eventually put his country's nuclear weapons on the negotiating table.
Speaking in Japan last week ahead of his visit to Pyeongchang for the Winter Olympics
, US Vice President Mike Pence said Washington plans to unveil what he called "toughest and most aggressive" sanctions yet against North Korea.
"Together with Japan, and all our allies, we will continue to intensify our maximum pressure campaign until North Korea takes concrete steps toward complete, verifiable and irreversible denuclearization," Pence said.
Pence did not specify if the sanctions would be unilateral or would be introduced to the UN Security Council.