Kyiv: Ukrainian forces will retreat from Severodonetsk after weeks of fierce fighting over the key city, a senior Ukrainian official said Friday, in a major boost to Russia's goal of seizing a swathe of eastern Ukraine.

The announcement came shortly after the European Union granted Ukraine candidate status in a show of support for the former Soviet republic, although there is still a long path ahead to membership.

Russia has focused its offensive on the Donbas region of eastern Ukraine after being repelled from the capital Kyiv and other areas following the February invasion. Its forces have gradually made progress despite encountering fierce resistance and sustaining heavy losses.

The strategically important industrial hub of Severodonetsk has been the scene of weeks of street battles as the outgunned Ukrainians put up a stubborn defence.

But Sergiy Gaiday, the governor of the Lugansk region which includes Severodonetsk, said that Ukrainian military forces in the city had received an order to withdraw.

"Remaining in positions that have been relentlessly shelled for months just doesn't make sense," he said on Telegram, adding that 90 percent of the city had been damaged.

The Ukrainians had already been pushed back from much of the city, leaving them in control of only industrial areas.

Capturing Severodonetsk and its twin city of Lysychansk would give the Russians control of Lugansk, and allow them to push further into the wider Donbas.

- Lysychansk under fire -

Gaiday said the Russians were now advancing on Lysychansk, which has been facing increasingly heavy Russian bombardment.

The situation for those that remain in the city is bleak.

Liliya Nesterenko said her house had no gas, water or electricity and she and her mother were cooking on a campfire. She was cycling along the street, and had come out to feed a friend's pets.

But the 39-year-old was upbeat about the city's defences: "I believe in our Ukrainian army, they should (be able to) cope."

A representative of pro-Russian separatists in Ukraine earlier told AFP that the resistance by Ukrainian forces trying to defend Lysychansk and Severodonetsk was "pointless and futile".

"At the rate our soldiers are going, very soon the whole territory of the Lugansk People's Republic will be liberated," said Andrei Marochko, a spokesman for the Moscow-backed army of Lugansk.

On Friday, Marochko said on Telegram that all the villages in the neighbouring areas of Zolote and Hirske were now under the control of Russian or pro-Russian forces.

In a video on Marochko's Telegram channel, a man in military clothing can be seen replacing the Ukrainian flag with the Zolote coat of arms with a hammer-and-sickle red flag.

Russia's defence ministry said on Friday that up to 2,000 people were "completely blocked" near Zolote and Hirske, and that around half of Zolote was under Russian control.

- Missiles hit university -

Russia has also intensified its offensive in the northern city of Kharkiv in the past few days.

An AFP team at the scene heard strong explosions in the city centre last night and in the morning saw that the Kharkiv Polytechnic Institute had been hit by missiles, breaking windows and causing its roof to partially collapse.

According to an unidentified military official at the scene, the Russians "thought there might be something military in there but there was not".

In the southern Kherson region, a Moscow-appointed official was killed by an explosive device planted in his car, Russian news agencies reported.

The Moscow-appointed deputy head of Kherson, Kirill Stremousov, said the regional head of the department of family, youth and sports had died "as a result of a terrorist act".

It was the first confirmed death of a pro-Russian official during a string of attacks on pro-Kremlin officials in Ukrainian regions under Russian control.

With Ukraine pleading for accelerated weapon deliveries, the United States announced it was sending another $450 million in fresh armaments, including HIMARS rocket systems, which can launch multiple missiles at extended range.

Ukraine's President Volodymyr Zelensky said on Twitter that Ukraine was "grateful" to US President Joe Biden for the decision.

"This support... is now more important than ever," he said.

- 'Future equal EU partner' -

At a Brussels summit Thursday, EU leaders granted candidate status to Ukraine, as well as Moldova.

Zelensky hailed the news as "a unique and historic moment".

"Today it is recognised that Ukraine is not a bridge, not a pillow between the West and Russia, not a buffer between Europe and Asia, not a sphere of influence," Zelensky said in a video address to Ukrainians on Friday.

"Ukraine is a future equal partner for at least 27 EU countries," he added.

Kremlin spokesman Dmitry Peskov dismissed Ukraine's new EU candidacy status as a "domestic European affair".

Russian President Vladimir Putin has strongly resisted what Moscow sees as attempts to bring the country into NATO.

But Ukraine's NATO aspirations are far from being realised and EU membership is at least years away.