KYIV — 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.

In Tokyo on Monday, President Joe Biden and Japanese Prime Minister Fumio Kishida joined in condemning Moscow’s invasion of Ukraine. Earlier on his trip to Asia, Biden signed legislation granting Ukraine $40 billion more in US support for its defense against the Russian attack.

Shelling increased in ferocity as Russian and Ukrainian forces battled along a 551-kilometer wedge of Ukraine’s eastern industrial heartland, driving residents to flee.

Polish President Andrzej Duda traveled to Kyiv on Sunday to support Ukraine’s European Union aspirations and addressed Ukraine’s parliament, receiving a standing ovation when he thanked the lawmakers for letting him speak where “the heart of a free, independent and democratic Ukraine beats.”

Ukraine does not have to yield to pressure from Russia and from elsewhere in Europe, Duda said. “I want to say clearly: Only Ukraine has the right to decide about its future.”

Duda said “Kyiv is the place from which one clearly sees that we need more America in Europe, both in the military and in this economic dimension.”

Poland has become an important ally of Ukraine, welcoming millions of Ukrainian refugees and becoming a gateway for Western humanitarian aid and weapons and a transit point for some foreign fighters who have volunteered to fight Russian forces.

Ukrainian President Volodymyr Zelenskyy called Duda’s visit, his second since April, “a historic opportunity not to lose such strong relations, built through blood, through Russian aggression. All this not to lose our state, not to lose our people.”

Zelenskyy has urged the 27-member EU to expedite his country’s request to join. It is to be discussed at a Brussels summit in late June.

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 ... engaging in a scorched-earth approach.”

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.

Zelenskyy said Sunday that 50 to 100 Ukrainian fighters were being killed, apparently each day, in the east.

The conflict is not confined to Ukraine’s east. Powerful explosions were heard early Monday in Korosten, about 160 kilometers west of Kyiv, the town’s deputy mayor said. (AP)