The leaders of the world’s biggest economies are scheduled to hold a video call with Ukrainian President Volodymyr Zelenskyy Sunday, in a show of unity the day before Russia marks its Victory Day holiday to honor the Soviet triumph over Nazi Germany on May 9.

The meeting of the Group of 7 nations comes after Zelenskyy warned in a late-night video address that Russian forces will likely intensify their attacks leading into Monday.

His comments came after the key Black Sea port of Odesa was hit with cruise missiles and the bombardment of the Azovstal steel plant up the coast in Mariupol continued Saturday.

All women, children, and elderly have been evacuated from the sprawling sites, Ukraine’s deputy prime minister said Saturday, but soldiers and civilian men remain in the facility where fighters are making their last stand to prevent Moscow’s complete takeover of the strategically important port city.

Elsewhere, preliminary information from a Russian airstrike on a school in the eastern Ukrainian village of Bilohorivka suggested 60 people had been killed, Luhansk Gov. Serhiy Haidai said in a post on his Telegram channel. NBC News has not been able to independently verify this.