SEOUL >> North Korea has shipped around 7,000 containers filled with munitions and other military equipment to Russia since last year to help support its war in Ukraine, South Korea’s defense minister said Monday.

Shin Won-sik shared the assessment at a news conference hours after the South Korean and Japanese militaries said the North fired multiple short-range ballistic missiles into its eastern waters, adding to a streak of weapons displays amid growing tensions with rivals.

Since the start of 2022, North Korea has used Russia’s invasion of Ukraine as a distraction to ramp up its weapons tests and has also aligned with Moscow over the conflict, as leader Kim Jong Un tries to break out of diplomatic isolation and join a united front against the United States.

U.S. and South Korean officials have accused North Korea of supplying Russia with artillery shells, missiles and other equipment in recent months to help fuel its war on Ukraine, saying that such arms transfers accelerated after a rare summit between Kim and Russian President Vladimir Putin in September.

North Korea in exchange possibly received badly needed food and economic aid and military assistance aimed at upgrading Kim’s forces, according to South Korean officials and private experts. Both Moscow and Pyongyang have denied the existence of an arms deal between the countries.

During a news conference in Seoul, Shin said the South Korean military believes the North, after initially relying on ships, has been increasingly using its rail networks to send arms supplies to Russia through their land border.

In exchange for sending possibly several million artillery shells and other supplies, North Korea has received more than 9,000 Russian containers likely filled with aid, Shin said. He raised suspicions that Russia could be providing North Korea with fuel, possibly in defiance of U.N. Security Council sanctions that tightly cap the country’s imports of oil and petroleum products.

While fuel shortages likely forced North Korea to scale back winter training activities for its soldiers in recent years, South Korea’s military assesses that the North expanded such drills this January and February, Shin said.

North Korea’s latest missile launches came days after the end of the latest South Korean-U.S. combined military drills that the North portrays as an invasion rehearsal.

Shin said the North may dial up its testing activity before the April 10 parliamentary elections in South Korea, which is shaping up as a confidence vote for conservative President Yoon Suk Yeol, who has taken a harder line than his liberal predecessor over North Korean nuclear ambitions and threats.

Animosity between the war-divided Koreans has recently worsened, with both countries taking steps to breach a 2018 bilateral military agreement on reducing border tensions. Kim vowed in January to abandon the North’s long-standing goal of reconciliation and to rewrite its constitution to declare the South its most hostile adversary.

While most of North Korea’s recent missile tests seem aligned with its stated goals of augmenting its frontline forces with new weapons systems, the South Korean and U.S. militaries are also evaluating whether some North Korean tests are aimed at verifying the performance of weapons it intends to send to Russia, Shin said.

North Korean state media said Monday that Kim sent a message of congratulations to Putin over his reelection as Russia’s president. On Saturday, Kim’s sister issued a statement through state media saying that her brother has used a Russian luxury limousine recently gifted by Putin and praised the car’s “special function,” in another effort to boost the visibility of the countries’ bilateral ties.