Fighting raged for the strategic Ukrainian city Lysychansk on Saturday, as Belarusian leader Alexander Lukashenko said his army had intercepted missiles fired on his territory by Kyiv's forces.

Ukraine denied claims by Moscow-backed separatists who said they had encircled Lysychansk, the last major city in the Lugansk area of the eastern Donbas region still in Kyiv's hands.

Lysychansk is located across the river from neighbouring Severodonetsk, which Russian forces seized last week.

The city's capture would allow Russian forces to push deeper into the Donbas, which has become the focus of their offensive since failing to capture Kyiv.

"Fighting rages around Lysychansk... The city has not been encircled and is under control of the Ukrainian army," Ruslan Muzytchuk, a spokesman for the Ukrainian National Guard, said on Ukrainian television.

Earlier in the day, Andrei Marochko, a spokesman for the separatist forces, told the TASS news agency: "Lysychansk is completely encircled."

Lukashenko on Saturday accused Ukraine of "provoking" neighbouring Belarus, saying his army intercepted missiles fired at his country by Ukrainian forces "around three days ago".

The claim came one week after Ukraine said missiles struck a border region from Belarus, a long-term Russian ally that supported the February 24 invasion.

But Lukashenko denied any involvement, which would represent an escalation of the conflict.

"As I said more than a year ago, we do not intend to fight in Ukraine," he was quoted as saying by state news agency Belta on Saturday.

Missiles continue to rain down across Ukraine, killing dozens.

Rockets struck residential properties in Sloviansk in the heart of the Donbas, killing a woman in her garden and wounding her husband, a neighbour told AFP Saturday, describing debris showered across the neighbourhood.

The witness said the strike on Friday was thought to use cluster munitions which spread over a large area before exploding, striking buildings and people who were outdoors.

Strikes on a southern resort town earlier Friday left 21 dead and dozens wounded after missiles slammed into flats and a recreation centre in Sergiyvka, 80 kilometres (50 miles) south of Black Sea port Odessa.

- 'Heavy losses' -

Victims of the Sergiyvka attacks included a 12-year-old boy, Ukrainian President Volodymyr Zelensky said in his daily address to the nation late Friday.

"I emphasise: this is an act of deliberate, purposeful Russian terror," Zelensky said.

Ukraine's chief diplomat Dmytro Kuleba said Saturday he had discussed a seventh round of European sanctions against Russia with his EU opposite number Josep Borrell.

Russian defence ministry spokesman Igor Konashenkov said Ukraine was "suffering heavy losses on all fronts", listing what he said were military targets across the country hit with artillery and missiles.

Earlier on Friday, Zelensky hailed a new chapter in its relationship with the European Union, after Brussels recently granted Ukraine candidate status in Kyiv's push to join the 27-member bloc, even if membership is likely years away.

The president of the European Commission Ursula von der Leyen said membership was "within reach" but urged them to work on anti-corruption reforms.

Norway, which is not an EU member, on Friday announced $1 billion worth of aid for Kyiv including for reconstruction and weapons.

And the Pentagon said it was sending a new armament package worth $820 million, including two air defence systems and more ammunition for precision rocket launchers.

- Soup spat -

In a decision that further cooled relations between Kyiv and Moscow, the UN's cultural agency inscribed Ukraine's tradition of cooking borshch soup on its list of endangered cultural heritage.

Ukraine considers the nourishing soup, usually made with beetroot, as a national dish although it is also widely consumed in Russia, other ex-Soviet countries and Poland.

UNESCO said the decision was approved after a fast-track process prompted by Russia's invasion of Ukraine.

We "will win both in the war of borshch and in this war," said Ukraine's Culture Minister Oleksandr Tkachenko on Telegram.

- 'Grains going to dry out' -

On Thursday, Russian troops abandoned their positions on Snake Island, which had become a symbol of Ukrainian resistance in the first days of the war, and sits beside shipping lanes near Odessa's port.

The Russian defence ministry described the retreat as "a gesture of goodwill" meant to demonstrate that Moscow will not interfere with UN efforts to organise protected grain exports from Ukraine.

But on Friday evening, Kyiv accused Moscow of carrying out strikes using incendiary phosphorus munitions on the rocky outcrop.

During a daily update, Russia's defence ministry made no comment on the alleged use of phosphorus.

In peacetime, Ukraine is a major agricultural exporter, but Russia's invasion has damaged farmland and seen Ukraine's ports seized, razed or blockaded -- sparking concerns about food shortages, particularly in poor countries.

Farmer Sergiy Lioubarsky, whose fields are close to the frontline, warned time was running out to harvest this year's crop.

"We can wait until August 10 at the latest, but after that, the grains are going to dry out and fall to the ground," he said.

Western powers have accused Putin of using the trapped harvest as a weapon to increase pressure on the international community, and Russia has been accused of stealing grain.