DONETSK, Ukraine: Shelling rocked the area around a key rebel base in the center of the insurgent bastion of Donetsk in eastern Ukraine Thursday, city authorities said.
Mortar fire erupted around the occupied regional headquarters of Ukraine's SBU security agency, the city council said in a statement, asking "everyone to get off the streets and seek shelter in a safe location."
An AFP journalist reported that heavy shelling could be heard mid-morning Thursday from central Donetsk.
Earlier local authorities said that artillery fire overnight killed three civilians and injured five more in the Budyonivsky district in the southeast of the million-strong industrial city.
The mortar blasts damaged three apartment blocks and five houses, the city council said in a statement.
Shelling also destroyed two houses in a village on the western outskirts of the mining hub but no casualties were reported, the statement said.
The latest deaths come as Ukraine's military says it is gearing up to retake the main insurgent bastion in the east, after a month of solid advances saw government forces encircle insurgents hunkered down there.
An airstrike hit near the centre of Donetsk for the first time Wednesday, stoking fears that the city's tree-lined streets could become the next battleground in Ukraine's almost four months of civil war that has killed over 1,300 people.
Civilians have been hit hardest, with more than 285,000 fleeing their homes, according to the U.N. refugee agency UNHCR, which warned of "a massive exodus" if fighting intensifies.
Across the region, local authorities in the second largest rebel bastion of Lugansk have warned of a looming "humanitarian catastrophe" as water, food and fuel supplies have dried up.
Ukraine's military meanwhile reported shelling overnight of four of its positions across the east, but no casualties.
In a bullish statement the military claimed that it appears the "fighting spirit of the terrorists has been broken."
Ukrainian forces said Wednesday that they had lost 18 soldiers in clashes with rebels over the preceding 24 hours, the highest daily death toll in weeks.