kyiv, Ukraine (AP) — Ukrainian President Volodymyr Zelenskyy said Tuesday that the thousands of North Korean troops expected to reinforce Russian troops on the front line in Ukraine are pushing the war of almost three years beyond the borders of the belligerents.

Western leaders say North Korea sent some 10,000 troops to aid Russia’s military campaign and warned that its involvement in a European war could also disrupt relations in the Indo-Pacific region, notably in Japan and Australia.

Zelenskyy said he spoke to South Korean President Yoon Suk Yeol and told him that 3,000 North Korean troops were already at military bases near the Ukrainian front line and that he expected this deployment increases to 12,000. South Korea, which is in close contact with NATO, the United States and the European Union over the latest developments, warned last week it could send weapons to Ukraine in retaliation for the North’s involvement.

“There is only one conclusion: this war is internationalized and goes beyond the borders” of Ukraine and Russia, Zelensky wrote on Telegram.

The Ukrainian president also said he agreed with Yeol to intensify cooperation between their countries and exchange more intelligence between them, as well as to develop concrete responses to Pyongyang’s involvement.

Meanwhile, North Korea said its top diplomat is visiting Russia in another sign of their deepening relationship.

Tensions on the Korean Peninsula are at their highest levels in years, with North Korea continuing a series of provocative weapons tests and South Korea and the United States expanding military exercises.

Russian drones, missiles and bombs crashed into kyiv and Kharkiv, Ukraine’s largest cities, in overnight attacks, killing four people and injuring 15 others. a continuous air attackauthorities announced Tuesday.

Russia has bombed civilian areas of Ukraine almost daily since its large-scale invasion of its neighbor, killing thousands.

The Russian army is also push hard against frontline defenses in the eastern Donetsk region of Ukraine. The Russian Defense Ministry said on Tuesday that Russian troops had captured the town of Hirnyk in Donetsk as well as the villages of Katerynivka and Bohoiavlenka.

Zelensky also spoke about the war during a meeting Tuesday in Reykjavik with the leaders of Denmark, Iceland, Finland, Norway and Sweden. He said a conference would begin Wednesday in Canada to address Russia’s kidnapping of what he said were tens of thousands of children from Ukraine’s occupied territories.

Russian air attack hits Kharkovin northeastern Ukraine around 3 a.m., hitting a house and killing four people, regional governor Oleh Syniehubov said. Nearly 20 houses were damaged in the attack, he said.

Hours earlier, Russia dropped a hover bomb on the iconic Derzhprom building in downtown Kharkiv, injuring seven people, Mayor Ihor Terekhov said. Derzhprom, also known as the Palace of Industry, is being considered for inclusion in the UNESCO World Heritage List.

Terekhov said Russia had focused its attacks on Kharkiv in recent days. He urged people not to ignore air raid warnings.

kyiv authorities said debris from intercepted Russian drones fell on two neighborhoods of the city, injuring six people.

Ukraine has also used long-range drones disrupt the Russian war machine and embarrass the Kremlin by striking targets on Russian soil.

A special forces academy in the Russian province of Chechnya was hit by drones, causing a fire that was quickly put out, according to Chechen leader Ramzan Kadyrov, a close ally of Russian President Vladimir Putin.

It was the first drone attack of the war against Chechnya, located about 800 kilometers (500 miles) east of Ukraine.

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Associated Press writer Jill Lawless in London contributed to this report.

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