Two years to the day from Russia's full-scale invasion of Ukraine, firefighters battled flames into the night.

Even after dawn, teams doused pockets of flames and stubborn embers in the building's roof. Smoke continued to billow skyward from a wrecked, elegant archway.

"I feel like it ripped me apart ... and not only the railway station," said a tearful Ruslana Popova, seated on the steps of a stairway crossing over the station's tracks.

"Well, I lived here," she added, managing a smile. "Just across, over there. We were neighbours. My aunt used to work here."

Police in Donetsk region, the focal point of Russia's advance in eastern Ukraine, said a guided aerial bomb hit the station about midnight. Four S-300 missiles targeted the town hours later.

Reuters could not verify battlefield reports from either side.

Kostiantynivka lies 30 km (18 miles) west of Bakhmut, a town that fell to Russian forces last May after months of battles, and north of Avdiivka, captured by Moscow's forces last week.

The station was all but destroyed in the attack, its facade and much of its roof collapsed from the overnight assault.

In the morning aftermath, workers cleared rubble from a supermarket that was also hit, all its windows smashed, much of its interior under piles of debris. The cupolas of a nearby church also sustained damage.

City officials pored over pieces of what was presumed to be the guided aerial bomb.

"I was asleep at night, I saw a bolt of light that lit up the whole town. That was it, I didn't hear any loud noise. When I woke up in the morning, I saw this nightmare," said Ksenia, standing in one of damaged buildings.

The station had been working, Ksenia said. She had bought a ticket last month and a humanitarian aid point was in operation.

"Why? I don't know, my parents are now left homeless, do you understand?" she said. "We lived together, we worked together as best we could. Now, we'll have to figure out what to do. We'll come up with something."

Russia's Defence Ministry said on Sunday that its forces had taken more advantageous positions near Avdiivka and the nearby town of Donetsk after President Vladimir Putin ordered the military to push further into Ukraine.

(Writing by Ron Popeski; Editing by Richard Chang)

By Vitalii Hnidyi