(Reuters) – Ukraine has ruled out a ceasefire or concessions to Moscow as Russia ramped up its offensive in the eastern Donbass region and halted gas supplies to Finland, as Polish President Andrzej Duda prepares to address Ukraine’s parliament on Sunday.

After ending weeks of resistance by the last Ukrainian fighters in the strategic southeastern city of Mariupol, Russia is launching a major offensive in Luhansk, one of two provinces in the Donbass.

The Russian-backed separatists were already in control of swathes of territory in Luhansk and the neighboring Donetsk region before the February 24 invasion, but Moscow wants to seize the last remaining Ukrainian-controlled territory in the Donbass.

“The situation in Donbass is very difficult,” Ukrainian President Volodymyr Zelensky said in his nightly speech. He said that the Russian army was trying to attack the cities of Sloviansk and Severodonetsk, but that Ukrainian forces were blocking their advance.

Zelensky’s adviser, Mikhailo Podolak, ruled out agreeing to a ceasefire and said Kyiv would not accept any agreement with Moscow that would include territorial concessions. He said that making concessions is counterproductive to Ukraine because Russia will respond more forcefully after any pause in fighting. Read more

“The war will not stop (after concessions). It will stop for a while,” Podolyak, Ukraine’s chief negotiator, told Reuters in an interview in a heavily guarded presidential office. “They will start a new attack, which will be more bloody and extensive.”

The latest calls for an immediate ceasefire came from US Defense Secretary Lloyd Austin and Italian Prime Minister Mario Draghi. Read more

The end of the fighting in Mariupol, the largest city captured by Russia, gave Russian President Vladimir Putin a rare victory after a series of setbacks in nearly three months of fighting.

Russia said the last Ukrainian forces that have holed up at the huge Azovstal steel mill in Mariupol surrendered on Friday. Read more

Full control of Mariupol gives Russia command of a land route linking Crimea, which Moscow captured in 2014, with mainland Russia and regions of eastern Ukraine controlled by pro-Russian separatists.

Ukrainian forces in the separatist-controlled Luhansk and Donetsk regions said on Saturday they had repelled nine attacks and destroyed five tanks and 10 other armored vehicles in the past 24 hours.

The Ukrainians said in a Facebook post that Russian forces were using aircraft, artillery, tanks, rockets, mortars and rockets along the entire front line to attack civilian buildings and residential areas. They said at least seven people were killed in the Donetsk region.

On Sunday, Britain’s Ministry of Defense said Russia was deploying BMP-T “Terminator” tank support vehicles in that attack. With only 10 available for the unit that had already incurred heavy losses in the failed attempt on Kyiv, the ministry said it was unlikely to have a significant impact.

Serhiy Gaidai, governor of the Luhansk region, said that Russian forces had destroyed a bridge over the Seversky Donets River between Severodonetsk and Lyschansk. He said in the messaging application Telegram that the fighting was taking place in the outskirts of Severodonetsk from morning until night.

Severodonetsk and its twin Lysichansk, across the Seversky Donets River, form the eastern part of a Ukrainian-held enclave that Russia has been trying to bypass since mid-April after it failed to capture Kyiv.

gas dispute

Russian state-owned gas company Gazprom (GAZP.MM)It said it had halted gas exports to Finland, which rejected Moscow’s demands to pay rubles for Russian gas after Western countries imposed sanctions over the invasion. Read more

Finland and Sweden on Wednesday applied to join the military alliance of NATO. Read more

Finnish gas wholesaler Jassum, the Finnish government and individual gas consuming companies in Finland have said they are ready to shut down Russian flows.

Most European supply contracts are made in euros or dollars. Last month, Moscow cut off gas to Bulgaria and Poland after they refused to comply with the new terms.

Western countries have also stepped up arms supplies to Ukraine. On Saturday, Kyiv got another big boost when US President Joe Biden signed a bill to provide nearly $40 billion in military, economic and humanitarian aid. Read more

Moscow says Western sanctions, along with arms shipments to Kyiv, amount to a “proxy war” by the United States and its allies. Thousands of people were killed in Ukraine in the war that displaced millions and destroyed cities.

Zelensky said he stressed the importance of more sanctions against Russia and the opening of Ukrainian ports in a phone call with Draghi on Saturday.

Duda’s office, which met with Zelensky in Kyiv last month, said he is the first foreign leader to address parliament in person since the invasion.

Additional reporting by Natalia Zenets, Max Hunder and Tom Palmforth in Kyiv and David Younggreen in Ottawa and Lydia Kelly in Melbourne and Reuters offices; writing by Madeleine Chambers, Richard Boleyn and Doina Chiako; Editing by Nick Ziminsky and Jerry Doyle

Our criteria: Thomson Reuters Trust Principles.