Russian troops have entered the outskirts of the Ukrainian city of Sievierodonetsk, the regional governor said on Monday, describing "very fierce" fighting in the ruins of a city that has become the focus of Moscow's offensive.
Russia has concentrated its firepower on the last major population center still held by Ukrainian forces in the eastern Luhansk province, in a push to achieve one of President Vladimir Putin's stated objectives after three months of war.
Incessant shelling has left Ukrainian forces defending ruins in Sievierodonetsk, but their refusal to withdraw has slowed the massive Russian offensive across the Donbas region.
Luhansk region governor Serhiy Gaidai said Russian troops had advanced into the city's southeastern and northeastern fringes. But he said Ukrainian forces had driven the Russians out of the village of Toshkivka to the south, potentially frustrating Moscow's push to encircle the area.
"Capturing Sievierodonetsk is a fundamental task for the occupiers ... We do all we can to hold this advance," Ukrainian President Volodymyr Zelenskiy said in a televised speech.
"Some 90% of buildings are damaged. More than two-thirds of the city's housing stock has been completely destroyed."
European Union leaders were due to meet on Monday and Tuesday to discuss a new sanctions package against Russia, potentially including an oil embargo.
But EU governments have been unable to reach agreement in a month of talks, with Hungary in particular saying it cannot afford to shut off the Russian oil that supplies its refineries through the huge Soviet-era Druzhba pipeline, whose name means "Friendship".
Ahead of the summit, German Economy Minister Robert Habeck expressed fears that EU unity was "starting to crumble". Draft conclusions, seen by Reuters, indicated there would be little in terms of new decisions.
But EU foreign policy chief Josep Borrell said that "there will be an agreement in the end", with a deal on the next sanctions package by Monday afternoon.
After failing to capture Kyiv in March, Russia announced that the focus of its "special military operation" was now to seize the entire Donbas region, consisting of two provinces, Luhansk and Donetsk, that Moscow claims on behalf of separatist proxies.
Russian Foreign Minister Sergei Lavrov on Sunday said the "liberation" of the Donbas was an "unconditional priority" for Moscow.
Capturing Sievierodonetsk and its twin city Lysychansk on the opposite bank of the Siverskyi Donets river would give Russia effective control of Luhansk province, a point at which the Kremlin might be able to declare some form of victory.
But by focusing its effort on a battle for the single small city - Sievierodonetsk housed only around 100,000 people before the war - Russia might be leaving other territory open to eventual Ukrainian counter-strikes.
The past few days have seen initial signs of a potential Ukrainian counteroffensive in the south, where Moscow is trying to consolidate its control of Kherson province, captured in the early weeks after it launched its invasion in February.
Kyiv says its forces pushed back Russian troops in recent days to defensive positions in three villages - Andriyivka, Lozove and Bilohorka - all located on the south bank of the Inhulets River that forms the border of Kherson.
The Institute for the Study of War think tank said this Ukrainian counterattack so far did not appear likely to retake substantial territory in the near term, but could disrupt Russian operations and force Moscow to reinforce the area.
Just to the north of the Kherson front, a suspected Russian strike damaged the center of the Ukrainian-held town of Novyi Buh overnight, the town council said on Telegram.
Russia said it had also struck a shipyard in Mykolayiv, a major Ukrainian-held port just west of Kherson.
Separately, French Foreign Affairs Minister Catherine Colonna was due to meet Zelenskiy in Kyiv later on Monday to offer more support, the French foreign affairs ministry said.
The Ukrainian government urged the West to provide more longer-range weapons to turn the tide in the war, now in its fourth month. Zelenskiy said he expected "good news" in the coming days.
A Ukrainian soldier on patrol in trenches near the town of Bakhmut, southwest of Sievierodonetsk, spoke of a nagging fear that his government could be drawn into negotiating an end to the conflict that would result in Ukraine losing territory.
"You know now what I'm most afraid of, now that the fighting is so intense, so tough?" Dmytro, a former English language teacher, told Reuters television. "That we would be told: That's it, stop it, we have a ceasefire."
"A negotiated settlement can only happen on Ukrainian terms, and at present if it happened it would be a horror."