KYIV, Ukraine, May 17, 2026 (BSS/AFP) - A wave of almost 600 Ukrainian drones attacked Russia overnight killing four people, authorities said on Sunday, as Ukrainian President Volodymyr Zelensky called the barrage an "entirely justified" retribution for Moscow's own pummelling of Ukraine.

Air defences shot down 556 drones overnight across the country, Russia's defence ministry said, with another 30 drones intercepted after dawn in one of the largest Ukrainian barrages of the ongoing conflict so far.

These interceptions -- far above the few dozen more often reported -- took place across 14 Russian regions, as well as the Crimean peninsula annexed from Ukraine and the Black and Azov seas, the ministry added.

Ukrainian President Volodymyr Zelensky said Kyiv's attack on Russia -- days after a massive drone and missile bombardment of the Ukrainian capital killed at least 24 people -- was "entirely justified".

"Our responses to Russia's prolongation of the war and its attacks on our cities and communities are entirely justified. This time, Ukrainian long-range sanctions reached the Moscow region, and we are clearly telling the Russians: their state must end its war."

Ukraine's defence ministry said that Moscow and the region "have experienced the largest-scale attack since the full-scale invasion began" in February 2022.

In Russia's capital region, "a woman was killed as a result of a UAV hitting a private house," governor Andrey Vorobyov posted on Telegram, adding that the early morning attack also claimed the lives of two men.

He added that four people were wounded and infrastructure facilities had been targeted.

Within the capital, local authorities reported that air defence systems had intercepted more than 80 drones overnight, wounding 12 people.

One of the strikes wounded construction workers at a job site near an oil and gas refinery, Mayor Sergei Sobyanin said.

"Refinery production has not been disrupted. Three residential buildings were damaged," he added.

While the capital region is often subjected to drone attacks, the city of Moscow, around 400 kilometres (250 miles) from the Ukrainian border, is less frequently targeted.

In the Belgorod region which borders Ukraine, one man was killed overnight in the Shebekino district in a drone attack on a lorry, regional authorities said.

The Ukrainian air force said meanwhile it had intercepted 279 Russian drones out of a total of 287 launched.

- Refinery, oil depot hit -

Diplomatic efforts to end the conflict have been at a standstill, with Kyiv unwilling to accept Moscow's maximalist demands for territory in the eastern Donbas region, saying it would be tantamount to surrender.

While the United States has pushed for both sides to come to the negotiating table, the talks have noticeably stalled since Washington's attention turned to the US-Israeli war on Iran in late February.

After the expiration of a US-brokered three-day truce on Tuesday to mark the anniversary of victory over Nazi Germany in World War II -- which both sides accused the other of violating -- Moscow and Kyiv have returned to trading attacks.

In response to daily bombardments by the Russian military for more than four years, Ukraine has regularly struck within Russia.

Kyiv frequently claims long-range strikes that it says target oil processing facilities in a bid to dent the oil revenues that fund Russia's war chest.

The latest attack on Sunday hit "the Moscow Oil Refinery, the Solnechnogorsk oil depot, and several microelectronics manufacturing facilities for the first time", Ukraine's defence ministry said on social media.

"The war is returning to where it came from," it added.

Kyiv's allies have accused Russia of mocking diplomatic efforts to end the conflict.