Seoul, South Korea — Russian President Vladimir Putin thanked North Korea for supporting his actions in Ukraine and said their countries will cooperate closely to overcome U.S.-led sanctions as he headed to Pyongyang on Tuesday for a summit with North Korean leader Kim Jong Un.

Putin's visit comes as tensions on the Korean Peninsula hit their highest point in years, with the pace of both Kim's weapons tests and the combined military exercises between the United States, South Korea and Japan intensifying in a cycle of tit-for-tat. The Koreas have also engaged in a Cold War-style psychological warfare that involved North Korea dropping tons of trash on the South with balloons and the South broadcasting anti-Korean propaganda broadcasts with its loudspeakers.

South Korea's military said soldiers fired warning shots to repel North Korean soldiers who temporarily crossed the rivals' land border Tuesday for the second time this month. The South's military said North Korea has been increasing construction activity in frontline border areas, such as installing suspected anti-tank barriers, reinforcing roads and planting landmines.

The countries are technically still at war, since the 1950-1953 conflict ended with an armistice. The Demilitarized Zone dividing them is one of the most heavily mined places on Earth.

But, Pyongyang is laying more landmines, reinforcing tactical roads and adding what look like anti-tank barriers, Seoul's military said, according to Agence France-Presse..

The agency reports that the South's Joint Chiefs of Staff said it believed Tuesday's incident -- like a previous one earlier this month -- was accidental, with some 20 to 30 North Korean troops carrying work tools involved. 

Putin's comments appeared in an op-ed piece in North Korean state media hours before he was expected to arrive in the North for a two-day visit as the countries deepen their alignment in the face of separate, intensifying confrontations with Washington.

Putin, who will be making his first visit to North Korea in 24 years, said he highly appreciates its firm support of his invasion of Ukraine. He said the countries would continue to "resolutely oppose" what he described as Western ambitions to "to hinder the establishment of a multi-polarized world order based on mutual respect for justice."

Putin also said Russia and North Korea will develop unspecified trade and payment systems "that are not controlled by the West" and jointly oppose sanctions against the countries, which he described as "unilateral and illegal restrictive measures."

North Korea is under heavy U.N. Security Council economic sanctions over its nuclear weapons and missile programs, while Russia is also grappling with sanctions by the United States and its Western partners over its aggression in Ukraine.

Putin said the countries will also expand cooperation in tourism, culture and education.

Putin's visit comes amid growing concerns about an arms arrangement in which Pyongyang provides Moscow with badly needed munitions to fuel Putin's war in Ukraine in exchange for economic assistance and technology transfers that would enhance the threat posed by Kim's nuclear weapons and missile program.

Military, economic and other exchanges between North Korea and Russia have sharply increased since Kim visited the Russian Far East in September for a meeting with Putin, their first since 2019.

U.S. and South Korean officials have accused the North of providing Russia with artillery, missiles and other military equipment to help prolong its fighting in Ukraine, possibly in return for key military technologies and aid. Both Pyongyang and Moscow have denied accusations about North Korean weapons transfers, which would violate multiple U.N. Security Council sanctions Russia previously endorsed.

Along with China, Russia has provided political cover for Kim's continuing efforts to advance his nuclear arsenal, repeatedly blocking U.S.-led efforts to impose fresh U.N. sanctions on the North over its weapons tests.

In March, a Russian veto at the United Nations ended monitoring of U.N. sanctions against North Korea over its nuclear program, prompting Western accusations that Moscow is seeking to avoid scrutiny as it buys weapons from Pyongyang for use in Ukraine.

Earlier this year, Putin sent Kim a high-end Aurus Senat limousine, which he had shown to the North Korean leader when they met for a summit in September. Observers said the shipment violated a U.N. resolution banning the supply of luxury items to North Korea.

John Kirby, spokesperson of the U.S. National Security Council, said the deepening relationship between Moscow and Pyongyang is concerning, "not just because of the impacts it's going to have on the Ukrainian people, because we know North Korean ballistic missiles are still being used to hit Ukrainian targets, but because there could be some reciprocity here that could affect security on the Korean Peninsula."

"We haven't seen the parameters of all of that right now, certainly haven't seen it come to fruition. But we're certainly going to be watching that very, very closely," he said.

Lim Soosuk, spokesperson of South Korea's Foreign Ministry, said Seoul has been stressing to Moscow that any cooperation between Russia and North Korea must not "proceed in a direction that violates U.N. Security Council resolutions or undermines peace and stability in the region."

Lim also reiterated Seoul's regret about Russia's decision to veto a U.N. resolution in March that effectively abolished monitoring by U.N. experts of Security Council sanction enforcement against North Korea. U.S. and South Korean officials have said they're discussing options for a new mechanism for monitoring the North.

Putin has continuously sought to rebuild ties with Pyongyang as part of efforts to restore his country's clout and its Soviet-era alliances. Moscow's ties with North Korea weakened after the 1991 Soviet collapse. Kim Jong Un first met with Putin in 2019 in Russia's eastern port of Vladivostok.

After North Korea, the Kremlin said Putin will also visit Vietnam on Wednesday and Thursday for talks that are expected to be focused on trade. The United States, which has spent years strengthening ties and accelerating trade with Vietnam, criticized Putin's planned visit.

"As Russia continues to seek international support to sustain its illegal and brutal war against Ukraine, we reiterate that no country should give Putin a platform to promote his war of aggression and otherwise allow him to normalize his atrocities," a U.S. Embassy spokesperson in Vietnam said in a statement.

In:
• Kim Jong Un
• South Korea
• Ukraine
• Russia
• Putin
• North Korea
• Vladimir Putin