*

Elderly bracing for worst winter in decades

*

Fears that attacks could target infrastructure

*

Families buy wood, mend windows, light stoves

By Tom Balmforth and Pavel Polityuk

KHARKIV, Ukraine, Oct 4 (Reuters) - In an abandoned tower block damaged by Russian shelling in Ukraine's second city, Olga Kobzar plans to tough out winter for as long as she can without electricity, water and central heating by lighting the gas stove in her kitchen for warmth.

The 70-year-old, who lives alone in a devastated district of northern Kharkiv where the temperature can fall to -20 Celsius (-4 Fahrenheit), is at the sharp end of what Ukrainian officials say will be the grimmest winter in decades.

She is the last remaining inhabitant of her tower block in the Saltivka district, around 30 km (20 miles) from the Russian border.

Her neighbour's flat was hit and others engulfed in flames, but hers is still intact, without basic utilities.

"It would be a sin to leave this place," she says, gesturing at shelves of old books and the portrait of her late husband she believes keeps her safe.

The seven-month-old war has wrought huge damage to the energy network - and to residential areas in swathes of Ukraine - and officials fear Moscow could deliberately attack critical infrastructure when the frost sets in.

Officials are urging people to stock up on everything from firewood to electric generators and fear disruptions to the centralised home-heating season that are hard to prepare for because so many different things could go wrong.

"Not everything depends on us - a lot depends on where the missiles land and what is destroyed. The aggressors want to doom us to a cold and dark winter," Kharkiv Mayor Ihor Terekhov said.

'PEOPLE ARE WORRIED'

Residential areas in cities are centrally-heated by power stations fuelled by natural gas, but heating apartment blocks with smashed windows and walls is dangerous because the pipes could freeze and wreck the local system.

The latest tally is 50,000 buildings and houses damaged during Russia's invasion as well as 350 of Ukraine's thousands of heating facilities, including several big ones, the minister for communities and territories development told a briefing on Monday.

Just a few blocks from Kobzar's flat, a priest, Viacheslav Koyun, is boarding up smashed windows for elderly neighbours so the heating can be turned on in their block.

"People are worried, the majority have left. We have literally five people in each stairwell. It's mainly pensioners, I've only stayed because it wouldn't be good to abandon the block and the pensioners," he says.