The aftermath of unusually intense shelling on the rebel stronghold, Donetsk.

Ukrainian government forces may be trying to achieve a breakthrough in fighting with pro-Russian separatists by Sunday, Ukraine's Independence Day.

Most of the shelling was on the city's outskirts but explosions were also heard in the city center.

At least three people were killed.

As government forces tighten their grip on rebels in the east, cities and towns face shortages of food and supplies.

Avdiivka, north of Donetsk, was retaken by the army in early August, but the fighting still goes on, and the city's cut off from all water and power.

(SOUNDBITE) (Russian) AVDIIVKA RESIDENT, OLEG, SAYING:

"There's no water, no electricity, nobody does anything. Pensions are not paid. The famine will start soon if it hasn't already."

The intensified shelling on Donetsk came just hours before German Chancellor Angela Merkel met with Ukraine's leaders in the capital Kiev.