Ukrainians were digging in to defend the eastern city of Sievierodonetsk as it endured heavy bombardment from Russian forces trying to take the industrial area known as the Donbas.

While Russian and Ukrainian forces battled along with a 551-kilometre wedge of Ukraine’s eastern industrial heartland, Polish President Andrzej Duda travelled to Kyiv on Sunday to support Ukraine’s European Union aspirations and addressed Ukraine’s parliament.

On the battlefield, grinding, town-by-town fighting continued as Russian troops try to expand the territory that Moscow-backed separatists have held since 2014 in the Donbas, which includes Luhansk and Donetsk.

Sievierodonetsk is the main city under Ukrainian control in Luhansk province, whose governor Serhii Haidai accused the Russians of “simply intentionally trying to destroy the city”.

Haidai said the Russians had occupied several towns and cities in Luhansk after indiscriminate, 24-hour shelling and were concentrating forces and weaponry there, bringing in troops from Kharkiv to the northwest, Mariupol to the south, and from inside Russia.

The sole working hospital in Sievierodonetck has only three doctors and supplies for 10 days, he said.

The Ukrainian military said Russian forces were unsuccessful in their attack on Oleksandrivka, a village outside the city. The conflict is not confined to Ukraine’s east. Powerful explosions were heard early Monday in Korosten, about 160 kilometres west of Kyiv.