Russia pounded Ukraine with hundreds of drones and dozens of missiles on Saturday, in the fourth major attack this month, targeting western cities and killing at least two people in Chernivtsi on the border with Romania.

President Volodymyr Zelenskiy said that Russia launched 597 drones and 26 missiles, killing two people, wounding 20, and damaging civilian infrastructure from Kharkiv and Sumy in the northeast to Lviv, Lutsk, and Chernivtsi in the west.

Ukrainian air defence units shot down 25 missiles and 319 Shahed drones and jammed 258 other drones with electronic warfare, the air force said.

"The pace of Russia’s aerial strikes demands swift decisions – and it can be curbed now by sanctions," Zelenskiy said on the Telegram app, issuing a fresh call for tough sanctions on Russia and more air defence for Ukraine.

"This war can only be stopped through strength. We expect not just signals from our partners, but actions that will save lives."

The attack is the latest in a series of massive aerial strikes over recent weeks. Russia has significantly ramped up its drones and missile strikes on Ukraine since June.

The UN Human Rights monitoring mission in Ukraine said that June saw the highest monthly civilian casualties in three years, with 232 killed and 1,343 injured.

Ukraine's Western cities of Lviv, Lutsk, and Chernivtsi suffered the most during the overnight attack, officials said.

Ruslan Zaparaniuk, the governor of the Chernivetskyi region, said that a 26-year-old woman and a 43-year-old man were killed and 14 others wounded as Russian drones and a missile struck the city, located about 40 km (24 miles) from Ukraine's border with Romania.

Several fires broke out across the city, and residential houses and administrative buildings were damaged, regional officials said.

In the city of Lviv, on Ukraine's border with Poland, 46 residential houses, a university building, the city's courts, and about 20 buildings housing small and medium-sized businesses were damaged in the attack, the mayor said.

"Windows and doors were blown out. Curtains fell, TV set was hurled. The apartment is covered in glass shards. It is horrible," Oleh Sidorov, 64, told Reuters in Lviv. "I want to clean the apartment. But I do not know how I will sleep during the night, there is no window."