Ukrainian officials issue an evacuation order for families with children from the city of Pokrovsk

KYIV: Ukrainian authorities on Monday ordered families with children to urgently evacuate the eastern city of Pokrovsk, where the Russian army is bearing down after a six-month slog across Ukraine's Donetsk region following the capture of Avdiivka.

Local authorities said Russian forces are advancing so quickly that families must leave the city and other nearby towns and villages. Some 53,000 people still live in Pokrovsk, officials say.

The relentless assault on Ukrainian strongholds in Donetsk and neighbouring Luhansk, which together make up the Donbas industrial region, has cost Russia heavily in troops and armour.

However, the onslaught has gradually paid dividends as Ukrainian defenders have no choice but to pull back from positions blown to pieces by Russian artillery, missiles and bombs.

One of Kyiv's attempts to ease the pressure was the August 6 incursion into Russia's Kursk region, opening an unexpected front in the hopes of unnerving the Kremlin and compelling it to split its military resources.

Ukrainian President Volodymyr Zelenskyy said Sunday the daring incursion is trying to create a buffer zone that might prevent further attacks by Moscow across the border, especially with long-range artillery, missiles and glide bombs.

That Ukrainian operation was continuing Monday under tight secrecy.

In Pokrovsk residents have just two weeks to leave the city safely, officials said in an interview with the US-funded Radio Liberty. Officials warned last week that Russian forces were rapidly advancing and were just 10 kilometres from the city's outskirts.

Oleksandr Syrskyi, Ukraine's Commander-in-Chief, said Monday that “heavy battles” were taking place in the Pokrovsk area.

The nearby town of Toretsk, whose capture would open the door for a Russian advance on the key stronghold of Chasiv Yar from the south, is also under heavy pressure, he said.

The Institute for the Study of War said Russian forces have been advancing roughly two square kilometres per day in the Pokrovsk region over the last six months.

They have relied on frontal infantry assaults from village to village, notching incremental progress as they make their manpower and materiel advantages tell, the Washington-based think tank said late Sunday.

Pokrovsk, which had a prewar population of about 60,000, is one of Ukraine's main defensive strongholds and a key logistics hub in the Donetsk region. Its capture would compromise Ukraine's defensive abilities and supply routes and would bring Russia closer to its stated aim of capturing the entire Donetsk region.

Pokrovsk officials were meeting with the residents to provide them with logistical details on the evacuation. People were offered shelter in western Ukraine, where they will be hosted in dormitories and separate houses prepared for them.