Ukraine sent waves of drones deep into western Russia in more than four hours of nighttime attacks that struck military assets, Russian officials and media reports said on August 30.

The drones hit an airport near Russia’s border with Estonia and Latvia, causing a huge blaze and damaging four Il-76 military transport planes, the Russian state news agency Tass reported, citing emergency officials.

With at least six regions targeted, the barrage appeared to be the most extensive Ukrainian drone attack on Russian soil since the war began 18 months ago, although no injuries were reported. The Kremlin has repeatedly accused Ukraine of cross-border incursions on the Belgorod region of Russia and of launching drones toward Moscow.

There was no immediate comment from Ukrainian officials, who usually don’t claim attacks inside Russia. The Kremlin’s forces, meanwhile, hit Kyiv with drones and missiles during the night in what Ukrainian officials called a “massive, combined attack” that killed two people.

Aerial attacks on Russia have escalated recently as Ukraine pursues a counteroffensive. Kyiv increasingly targets Russia’s military assets behind the front lines in eastern and southern Ukraine.

Ukraine has also claimed to have used naval drones against Russian ships in the Black Sea. Ukrainian media said Kyiv saboteurs used drones last week to hit bomber aircraft parked at air bases deep inside Russia.

The airport in the Pskov region, about 700 kilometers (400 miles) north of the Ukrainian border and 700 kilometers (400 miles) west of Moscow, suffered the most damage in the overnight attacks.

Smoke from a massive fire billowed over the city of Pskov, the region’s namesake capital, according to social media posts, including video of loud bangs and flashes, along with the crackle of air defense systems and tracers in the night sky.

Pskov Gov. Mikhail Vedernikov ordered all flights to and from the airport canceled for the day to assess damage, which he later said was not major, adding that normal operations would resume Thursday.

Other regions hit were Oryol, 400 kilometers (240 miles) south of Moscow, as well as Ryazan and Kaluga, which are both 200 kilometers (120 miles) south of the capital. Also hit was Bryansk, which borders Ukraine, according to the Russia Defense Ministry.

Three main Moscow airports — Sheremetyevo, Vnukovo and Domodedovo — temporarily halted incoming and outgoing flights.

The Associated Press was unable to confirm whether the drones were launched from Ukraine or inside Russia.

Mykhailo Fedorov, Ukraine’s minister of digital transformation, said his country has drones with a range of up to 500 kilometers (300 miles), although he did not take responsibility for any attacks in Russia or Crimea, the peninsula that Russia illegally annexed from Ukraine in 2014.

“If you look carefully at the news recently, in general, every day there are news about long-range drones that hit various targets both in occupied Crimea and in the territory of Russia,” Mr. Fedorov told AP recently. ”So in this regard, let’s say, that more or less a mass production of these drones has appeared.”

Kremlin spokesman Dmitry Peskov said the Russian military would undoubtedly analyze “how this was done in order to take appropriate measures to prevent these situations in the future.”

Firing at distant Russian targets could reflect a Ukrainian tactic of stretching the Kremlin’s military resources as Moscow scrambles to buttress its air defenses, said Douglas Barrie, senior fellow for military aerospace at the International Institute for Strategic Studies.

“Putting air defense systems there means you can’t put them somewhere else,” he told AP. “This draws on Russian capability.”

Russia’s Foreign Ministry spokeswoman Maria Zakharova said Ukraine was relying on foreign help because the drones “simply would not be able to fly such a distance without carefully researched information from Western satellites.”

Russian state TV largely ignored the strikes, aside from a brief mention of the Pskov fire. But Russia 1’s popular political talk show “60 Minutes” opened with the attacks. It showed videos of the Pskov fire and blasts in Bryansk that had flooded social media, along with a soundtrack of sinister music.

Russia, meanwhile, also used drones as well as missiles in its biggest bombardment of Kyiv in months, Ukrainian authorities said.

Two security guards, aged 26 and 36, were killed and another person was injured by falling debris, said Serhiy Popko, head of Kyiv’s military administration, posting on Telegram.

Russia launched Iranian-made Shahed exploding drones at the capital from various directions, followed by air-launched missiles, Popko said. It was unclear how many were fired, but Popko called it the biggest attack on the capital since spring.

Kyiv resident Iryna Oblat pointed to debris in the street and shattered windows in surrounding buildings.

“Look where it hit, look what happened to the house,” she said. “Garages are on fire. We don’t know how many cars and garages were destroyed because firefighters and police won’t let us in.”

Also on Wednesday, Russia-installed officials in Crimea reported repelling an attack of drones targeting Sevastopol’s harbor. Past drone attacks have hit fuel depots and airfields in Crimea or Russian-held areas of Ukraine.

Late that same day, the Kremlin-appointed leader of Crimea claimed that a Ukrainian cruise missile was downed over the peninsula’s eastern part, with falling debris damaging a power line. Regional officials in Russia’s Bryansk province also claimed that nine drones were brought down on over its territory on Wednesday.

In Ukraine, explosions were reported in the southern city of Odesa and the Cherkasy region.

Ukraine’s air defenses destroyed 28 cruise missiles and 15 of 16 Shahed drones targeting Kyiv and multiple regions across the country overnight, the air force said in its daily Telegram update.

The White House, meanwhile, said it has new intelligence that shows Russian President Vladimir Putin and North Korean leader Kim Jong Un have swapped letters as Moscow looks to Pyongyang for munitions for the war.

National Security Council spokesman John Kirby detailed the finding just weeks after the White House said it determined that Russian Defense Minister Sergei Shoigu, during a recent visit to Pyongyang, called on North Korea to increase munitions sales to Moscow. Russia wants additional artillery shells and other basic materiel, Kirby said.