A new round of Moscow's shelling and drone attacks killed six people and wounded dozens in Ukraine Sunday, authorities said, while Kyiv hit two oil refineries deep inside Russia.  

There was no reduction in hostilities on the frontline, even as the United States and Russia agreed to hold a summit in a bid to resolve the conflict, which so far does not include Ukraine. 

"Russia has not taken a single real step towards peace, not a single step on the ground or in the air that could save lives," Ukrainian President Volodymyr Zelensky said in a regular evening address on Sunday.

Six people died across the eastern regions of Donetsk, Zaporizhzhia, and Kherson, their respective authorities said. 

The focus of the Russian offensive is on eastern Ukraine, where it has stepped up gains in recent months against its less well-equipped opponents.

A Russian glide bomb hit a busy bus station in the city of Zaporizhzhia in a separate afternoon strike, wounding 19 people at once, the local officials said, adding that a search and rescue operation was still ongoing. 

Visuals from the site shared by the authorities showed rescuers with sniffer dogs pulling injured people in blood stains and dust from the rubble in the shattered central bus station building.    

Three beachgoers were killed earlier in the Black Sea coastal city of Odesa, after they triggered a mine while swimming in a prohibited area.  

The Ukrainian army claimed its drones had hit a large oil refinery in Russia's western Saratov region. Its governor Roman Busargin only gave a vague comment about it, saying that "one of the industrial enterprises was damaged" and adding that one person died as a result of the drone attack. 

Another refinery was damaged in Russia's remote northern town of Ukhta in the Komi Republic, some 2,000 kilometers (1,200 miles) from the frontline, a source in Ukraine's GUR main intelligence directorate told AFP. 

The Komi governor confirmed in his Telegram channel there was a drone attack on the region, but didn't mention the Ukhta refinery and said there were no casualties in the assault. 

Another woman died in Russia's Belgorod region, often under Ukrainian fire due to its proximity to the frontline, the local governor said. 

Kyiv is trying to hamper Moscow's ability to fund the more than three-year war of attrition by attacking its oil and gas facilities, the key source of revenue for the state budget.    

Ukraine's military claimed to have taken back the village of Bezsalivka in the Sumy region from the Russian army, which has made significant recent gains.

Presidents Vladimir Putin and Donald Trump will meet in the US state of Alaska this Friday to try to resolve the grinding conflict, despite warnings from Ukraine and Europe that Kyiv must be part of negotiations.