Shelling is resounding on the outskirts of a Ukrainian port city as Russian-backed rebels press their offensive in the strategically key southeast just hours ahead of talks that are widely hoped to bring a cease-fire.

Associated Press reporters heard heavy shelling on Friday morning north and east of Mariupol. The city lies along the Sea of Azov, between Russia to the east and the Russia-annexed Crimean Peninsula to the west. Seizure of the city would give the rebels a strong foothold.

Representatives of Ukraine, Russia, the rebels and the Organization for Security and Cooperation in Europe are to meet later Friday in Minsk, Belarus, for talks on ending the conflict. Both Ukraine's president and rebel leaders say they are prepared for a cease-fire if the talks succeed.