Russian Foreign Minister Sergey Lavrov arrived in North Korea on Wednesday, according to Russian state news agency Tass, the latest in a flurry of diplomatic activity between the two countries in which Russian Defense Minister Sergei Shoigu visited North Korea in July and North Korean leader Kim Jong Un traveled to Russia in September.

Earlier in the week, Lavrov accompanied President Vladimir Putin on a visit to Beijing that underscored Chinese support for Moscow during its war in Ukraine.

Lavrov last visited North Korea in 2018. During his two-day visit he is to meet with North Korean Foreign Minister Choe Son Hui, Russian state news agency RIA Novosti said. Putin also accepted an invitation from Kim to visit North Korea, but the timing has not been announced.

During Kim’s visit to Russia he met Putin at Russia’s Vostochny Cosmodrome and inspected fighter jets at an aircraft factory in Russia’s far east.

The White House said on Friday that North Korea has delivered more than 1,000 containers of military equipment and munitions to Russia for its ongoing war in Ukraine.

Speculation about a possible North Korean plan to refill Russian munition stores drained by its protracted war with Ukraine flared during Kim’s visit to Russia.

White House National Security Council spokesman John Kirby said the U.S. believes Kim is seeking sophisticated Russian weapons technologies in return for the munitions to boost North Korea’s military and nuclear program.

Kim called last month for an exponential increase in production of nuclear weapons and for his country to play a larger role in a coalition of nations confronting the United States in a “new Cold War,” North Korean state media said.

During Kim’s six-day trip to Russia, his longest foreign travel as a leader, the two countries said they discussed boosting their defense ties but didn’t disclose any specific steps. Foreign experts speculate the two countries, both locked in confrontations with the West, were pushing to reach arms transfer deals in violation of U.N. Security Council resolutions.

The trip to Russia was also Kim’s first foreign trip since the pandemic, during which North Korea imposed tight border controls for more than three years. After decades of hot-and-cold relations, Russia and North Korea have drawn closer since Moscow’s invasion of Ukraine in 2022.

Relations between Russia and North Korea go back to the North’s foundation in 1948, as Soviet officials installed young, ambitious nationalist Kim Il Sung, Kim’s late grandfather, as the country’s first ruler. Soviet aid shipments were crucial in keeping North Korea’s economy afloat for decades before the disintegration of the Soviet Union in the early 1990s.