Ukrainian forces battling Russian troops in a key eastern city appear on the cusp of retreat, although the regional governor insisted they were still fighting “for every centimetre” of the city.

The urban battle for Sievierodonetsk testifies to the painstaking, inch-by-inch advance by Russian forces as they close in on control of the entire Luhansk region, one of two that make up the industrial heartland known as the Donbas.

After a bungled attempt to overrun Kyiv in the early days of the war, Russia shifted its focus to the region of coal mines and factories.

The region has been partly controlled by Russia-backed separatists for years, making supply lines shorter and allowing Moscow to tap separatist forces to back its offensive.

But Russia also faces Ukraine’s most battle-hardened troops, who have been fighting the separatists for eight years there.

The result is a slow slog with both sides exchanging artillery barrages that seemingly inflict heavy losses and neither appearing to have the clear momentum.

Luhansk governor Serhiy Haidai acknowledged the difficulties in Sievierodonetsk on Wednesday, saying “maybe we will have to retreat, but right now battles are ongoing in the city”.

Earlier, on the Telegram messaging app, he said Ukrainian forces were fighting “for every centimetre of the city”.

He indicated that they could pull back to positions that were easier to defend. The city across the river, Lysychansk, sits on higher ground.

Sievierodonetsk became the administrative capital of the region after the city of Luhansk was taken by separatists in 2014. Both it and Lysychansk are wedged between Russian forces to the east, north and south, and are among a few cities and towns in Luhansk still holding out.

The Kremlin has claimed its forces hold nearly all of the Luhansk region, and about half of the Donetsk region that rounds out the Donbas.

Meanwhile, to the north, Russian shelling of the northern Kharkiv region killed five people and wounded 12 more over the past 24 hours, regional governor Oleh Syniehubov said on Wednesday.

And the Russian military said that Moscow had used “air-launched, high-precision missiles” to hit an armour repair plant near Kharkiv. There was no confirmation from Ukrainian officials of such a plant being hit.

Before Russia’s February 24 invasion, Ukrainian officials said Russia controlled some 7% of the country, including the Crimean Peninsula, which Russia annexed in 2014, and areas held by the separatists in Donetsk and Luhansk. Last week, Ukrainian president Volodymyr Zelensky said Russian forces held 20% of the country.

While Russia has superior firepower, the Ukrainian defenders are entrenched and have shown the ability to counterattack.

“The absolutely heroic defence of the Donbas continues,” Mr Zelensky said late on Tuesday in his nightly video address.

Speaking earlier to a Financial Times conference, Mr Zelensky insisted on Ukraine’s need to defeat Russia on the battlefield but also said he was still open to peace talks with Russian president Vladimir Putin.

On the diplomatic front, Russian foreign minister Sergey Lavrov held talks on Wednesday with Turkish officials on a plan that could allow Ukraine to export its grain through the Black Sea to global markets amid an escalating global food crisis.