KYIV, Ukraine — Russia launched almost 500 drones at Ukraine in the biggest overnight drone bombardment of the three-year war, the Ukrainian air force said Monday, as the Kremlin presses its summer offensive amid direct peace talks that have yet to deliver progress on stopping the fighting.

As well as 479 drones, 20 missiles of various types were fired at different parts of Ukraine, according to the air force, which said the barrage targeted mainly central and western areas of Ukraine.

Ukraine’s air force said its air defenses destroyed 277 drones and 19 missiles in mid-flight on Sunday night, claiming that only 10 drones or missiles hit their target. Officials said one person was injured. It was not possible to independently verify the claims.

A recent escalation in aerial attacks has coincided with a renewed Russian battlefield push on eastern and northeastern parts of the roughly 620-mile front line.

Ukraine’s President Volodymyr Zelenskyy said late Sunday that in some of those areas “the situation is very difficult.” He provided no details.

Ukraine is short-handed on the front line against its bigger enemy and needs further military support from its Western partners, especially air defenses. But uncertainty about the U.S. policy on the war has fueled doubts about how much help Kyiv can count on.

Ukraine has produced some stunning counter-punches, however. Its recent drone attack on distant Russian air bases was unprecedented in its scope and sophistication.

The Ukrainian General Staff claimed Monday that special operations forces struck two Russian fighter jets stationed at the Savasleyka airfield in Russia’s Nizhny Novgorod region located some 650 kilometers northeast from the Ukrainian border. The statement did not say how the planes were hit. There was no immediate comment on the claim from the Russian authorities. Some Russian war bloggers said there was no damage to the warplanes.

Russian officials have said the recent intensified assaults are part of a series of retaliations for Ukraine’s strike on air bases that were hosting nuclear-capable strategic bombers. A strike on a Ukrainian air base in Dubno, in the western Rivne region, was one such response, the Russian Defense Ministry said Monday.

Two recent rounds of direct peace talks between Russian and Ukrainian delegations in Istanbul have yielded no significant breakthroughs beyond pledges to swap prisoners as well as thousands of their dead and seriously wounded troops. Russian President Vladimir Putin has indicated he will keep fighting until his conditions are met.

The exchange of hundreds of soldiers and civilians has been a small sign of cooperation in otherwise failed efforts to agree on a ceasefire.

More prisoners were swapped Monday in a staggered process taking place over coming days, Zelenskyy and the Russian Defense Ministry announced, though neither side said how many. Those swapped included wounded and seriously wounded soldiers, as well as those under 25, Zelenskyy said. “The process is quite complicated, there are many sensitive details, negotiations continue virtually every day,” he added.

But the two sides have disagreed over the transfer of soldiers killed in action. The Russian Defense Ministry alleged that Ukraine over the weekend failed to pick up the bodies of its fallen soldiers that Russia made available for collection.

But Zelenskyy claimed that Moscow hadn’t sent to Kyiv the names of more than 1,000 Ukrainians whose bodies are currently in Russian-controlled territories, as had been agreed. He accused Russian authorities of playing “dirty” games.

Even so, Kremlin spokesman Dmitry Peskov said Monday the swap is expected to go ahead, although he said there were no specific arrangements so far for the transfer.

Ukraine’s intelligence chief, Kyrylo Budanov, said the exchange of soldiers’ bodies will begin this week.

Russia has repeatedly targeted civilian areas of Ukraine with Shahed drones during the war, as happened on Sunday night. The attacks have killed more that 12,000 Ukrainian civilians, according to the United Nations. Russia says it only attacks military targets.

Ukraine has developed long-range drones that continue to strike deep inside Russia.

Russia’s Ministry of Defense said Monday that it shot down 49 Ukrainian drones overnight over seven Russian regions.

Two drones hit a plant specializing in electronic warfare equipment in the Chuvashia region, located more than 370 miles east of Moscow, local officials reported.

Alexander Gusev, head of Russia’s Voronezh region, said that 25 drones had been shot down there overnight, damaging a gas pipeline and sparking a small fire.