A massive drone strike rattled Moscow and its suburbs overnight into Sunday, injuring several people and temporarily halting traffic at some of Russia's busiest airports, officials reported. Meanwhile, a huge nighttime wave of Russian drones targeted Ukraine.

This came after Russian President Vladimir Putin signed into law a pact with North Korea Saturday night, obliging the two countries to provide immediate military aid using “all means” if either is attacked. The agreement marks the strongest link between Moscow and Pyongyang since the end of the Cold War.

Earlier this week, Ukraine reported that its troops engaged for the first time with North Korean units. U.S. officials earlier confirmed the deployment of at least 3,000 North Korean troops to Russia, while Kyiv has repeatedly said the number is far higher. This has fueled concerns of a marked escalation in Moscow's war on Ukraine, and tensions spilling over into the Asia-Pacific.

Both Moscow and Kyiv have kept a tight lid on casualty figures since the start of the full-scale war despite regular reports of Russian forces taking huge losses following “human wave” attacks that aim to exhaust Ukrainian defenses.

However, the chief of the UK defense staff, Tony Radakin, told the BBC that Russian forces had suffered their worst month of casualties in October since the full-scale invasion of Ukraine in February 2022. He said Moscow’s troops suffered an average of 1,500 dead and wounded per day, bringing their total losses in the war to 700,000.

According to Radakin, ordinary Russians were paying “an extraordinary price” for the war, even as a grueling, monthslong Russian offensive in Ukraine’s industrial east continues to eke out gains. He did not say how UK officials had calculated the Russian casualty figures.

“There is no doubt that Russia is making tactical, territorial gains and that is putting pressure on Ukraine,” he said. But he added that they were “tiny increments of land,” and Moscow’s mounting defense and security spending was putting an increasing strain on the country.

Radakin insisted that Ukraine’s Western partners should stand by it for “as long as it takes” to beat back Russian aggression, even as allies of U.S. President-elect Donald Trump have signaled that Kyiv may have to cede territory to seek peace.

On Sunday, the Kremlin’s official spokesman voiced cautious optimism about Trump’s upcoming presidency, saying: “At least he talks about peace. … He does not talk about confrontation.”

“The signals are positive. Trump, during his election campaign, said that he perceives everything through deals, that he can make deals that will lead everyone toward peace,” Dmitry Peskov told reporters at a briefing.

“He does not talk about a desire to inflict a strategic defeat on Russia, and this favorably distinguishes him from the current (U.S.) administration,” Peskov said.

But Ukrainian President Volodymyr Zelenskyy on Sunday insisted that “strong decisions” from Kyiv’s Western partners are needed to stop the “terror” of Russian drone and missile strikes, and secure “reliable peace” for Ukraine.

“The killing of children, the loss of family members cannot simply be forgotten,” Zelenskyy said in a post on the Telegram messaging app.

“Without strong decisions, there is no security from terror, and this is equally clear in every country. There is no reliable peace without justice,” he said.

Fierce fighting has continued near the eastern Ukrainian cities of Toretsk and Kurakhove, Ukraine’s General Staff reported Sunday. Between 700 and 1,000 residents remain in Kurakhove, a front-line city surrounded on three sides and battered into ruin. Most of them live underground with no running water, heating or electricity.

Meanwhile, Russia’s Defense Ministry said a total of 84 Ukrainian drones were shot down overnight in Russian territory, following what it called a “mass strike on civilian infrastructure." A man died under rubble after drones struck his apartment block in Russia’s Belgorod region, just kilometers from the Ukrainian border, local Gov. Vyacheslav Gladkov reported.

Five other people were injured in the Moscow suburb of Ramenskoe and a nearby village, according to local officials. Russian channels on the messaging app Telegram carried eyewitness reports of drone debris setting fire to suburban homes.

Russia's aviation authority said flights were briefly grounded at major international airports including Sheremetyevo and Domodedovo. At least 14 flights bound for Moscow were rerouted to Nizhnyi Novgorod, a city over 490 kilometers (300 miles) east, airport representatives there reported.

Ukraine’s General Staff claimed on Sunday that Ukrainian drones caused a fire at an arms depot in Russia’s southern Bryansk region, near Ukraine and Belarus. The online update featured a photo showing thick plumes of reddish smoke rising into the night sky. The AP could not verify the circumstances in which it was taken, and there was no immediate comment from Russia.

Separately, Russia’s emergencies ministry on Sunday said that a major fire broke out at a warehouse outside of Moscow. There were no immediate reports of casualties, and it was not clear whether the blaze was linked to the Ukrainian drone strikes.

Russia overnight launched a “record” 145 drones at Ukrainian territory, according to Ukraine’s air force, 62 of which were shot down. A further 67 were “lost,” the air force said, a likely reference to electronic jamming that caused the drones to veer off course.

At least one person was injured as Russian drones struck residential areas in Ukraine’s southern port of Odesa, local Gov. Oleh Kiper reported. And at least five civilians, including a 17-year-old girl and 10-year-old boy, were injured by falling drone debris and shelling in Ukraine’s northeastern Kharkiv region Sunday, its Gov. Oleh Syniehubov and local prosecutors said.

Russia later on Sunday said that it had struck a large deployment of Ukrainian soldiers in the Kharkiv province with thermobaric rockets, but didn't immediately provide evidence.