Russia unleashed a massive daytime drone attack on Ukraine on Wednesday, targeting critical infrastructure in the west, killing at least six people and prompting NATO-member Poland to scramble fighter jets, officials said.

Hungary, now led by a government more in line with the European mainstream, condemned the strikes on areas of Ukraine with ethnic Hungarian communities and summoned the Russian ambassador. Ukrainian President Volodymyr Zelenskiy praised the Hungarian action as an “important message”.

Zelenskiy, writing on Telegram while attending a security conference in Romania, said the Russian attack was continuing through the evening, with Moscow now deploying missiles.

Zelenskiy had earlier said that since midnight Moscow had launched at least 800 drones, with the attack deliberately targeting regions closest to the borders of NATO countries.

“It certainly cannot be called a coincidence that one of the longest massive Russian attacks against Ukraine takes place precisely at the time when the President of the United States arrived for a visit to China,” Zelenskiy said on Telegram.

Zelenskiy said that six people were killed and dozens injured in the attack, which spanned other regions. Ukraine’s railway infrastructure was struck 23 times during the barrage, a presidential advisor said, though traffic was maintained.

It was the first such major attack after a three-day U.S.-brokered ceasefire between Ukraine and Russia, which ended on Monday.

Poland scrambled fighter jets as a preventative measure due to the Russian air strikes on Ukraine, the Polish army said.

Hungarian Prime Minister Peter Magyar, speaking after the new government’s first cabinet meeting, said the Russian ambassador had been summoned to the foreign ministry on Thursday morning to meet foreign minister Anita Orban.

Orban will condemn the attack at the meeting and ask the ambassador when Russia plans to end the more than four-year-old war, he added. Under the outgoing government voted out of office this month, Hungary blocked aid for Ukraine and tried to slow its efforts to join the EU.