SOLEDAR, Ukraine - Ukraine marked 100 days since Moscow's invasion on Friday with Russian forces hammering the Donbas in their push to capture the country's east.

The somber milestone came less than 24 hours after Kyiv announced Moscow was now in control of 20 percent of Ukrainian territory, including Crimea and parts of the Donbas seized in 2014.

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After being repelled from around the capital, President Vladimir Putin's troops have set their sights on capturing eastern Ukraine, prompting dire warnings the war could drag on.

Following White House talks with US President Joe Biden, NATO chief Jens Stoltenberg warned Thursday that Ukraine's allies needed to brace for a gruelling "war of attrition".

"We just have to be prepared for the long haul," Stoltenberg said, while reiterating that NATO does not want direct confrontation with Russia.

While the advance has been much slower than Moscow expected, Russian forces have expanded control beyond the 43,000 square kilometres (16,600 square miles).

"Today, about 20 percent of our territory is under the control of the occupiers," Ukrainian President Volodymyr Zelensky said in an address to Luxembourg lawmakers.

Since Russia's February 24 invasion, thousands of people have been killed and millions forced to flee, with Ukraine's east now bearing the brunt of Russia's assault, which Zelensky said was killing up to 100 Ukrainian soldiers every day.

On the ground, street battles were raging in the industrial hub of Severodonetsk in Lugansk, part of the Donbas.

The strategic city is a key target for Moscow, which already controls 80 percent of the area, but Lugansk regional governor Sergiy Gaiday vowed Ukrainian forces would fight "until the end".

Severodonetsk's Azot factory, one of Europe's biggest chemical plants, was targeted by Russian soldiers who fired on one of its administrative buildings and a warehouse where methanol was stored.

'Shooting is everywhere'

Ukrainian troops were still holding an industrial zone, Gaiday said, a situation reminiscent of Mariupol, where a huge steel works was the southeastern port city's last holdout until Ukrainian troops finally surrendered in late May.

In the city of Sloviansk, about 80 kilometers (50 miles) from Severodonetsk, residents recounted constant bombardments by Russian troops.

Paramedic Ekaterina Perednenko, 24, said she had only just returned to the city five days ago but realizes that she will have to leave again.

"It's very difficult here. Shooting is everywhere, it's scary. No water, electricity or gas," she said.

Retiree Leonid, 79, said he was also leaving the city and would seek refuge elsewhere in Europe.

"I feel pain. The most prominent feeling I have is that we didn't deserve this. We don't understand why we are punished like this," he said.

Valeriy Zaluzhnyi, the commander in chief of Ukraine's armed forces, pleaded for modern armaments from NATO, saying that "the enemy has a decisive advantage in artillery."

"It will save the lives of our people," he added.

Financial squeeze

Led by the United States, Western nations have pumped arms and military supplies into Ukraine to help it survive the onslaught so far.

Bridget Brink, the new US ambassador to Kyiv, promised Thursday that the United States would "help Ukraine prevail against Russian aggression," after presenting her credentials to Zelensky.

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Earlier this week, the United States announced that it was sending more advanced, Himar multiple rocket launch systems to Ukraine.

The mobile units can simultaneously fire multiple precision-guided munitions up to 80 kilometers away.

They are the centerpiece of a $700 million package that includes air-surveillance radar, more Javelin short-range anti-tank missiles, artillery ammunition, helicopters, vehicles and spare parts.

Kremlin spokesman Dmitry Peskov accused Washington of "adding fuel to the fire," although US officials insist Ukraine has promised not to use them to strike inside Russia.

Beyond sending arms to Ukraine, Western allies have also sought to choke off Russia's financial lifeline in a bid to get Putin to change course.

Ramping up an already long list of embargoes, the United States blacklisted Putin's money manager and a Monaco company that provides luxury yachts to Moscow's elite.

Across the Atlantic, EU nations agreed new sanctions that would halt 90 percent of Russian oil imports to the bloc by the end of the year.

Hunger crisis

Russia warned that European consumers would be the first to pay the price for the partial oil embargo.

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But some relief was in view for the overheated oil market as producers including Saudi Arabia agreed to add 648,000 barrels per day to the market in July, up from 432,000.

The war has wrecked Ukraine's economy, forcing the central bank to more than double its key interest rate on Thursday to prop up the hryvnia.

But it carries far wider consequences too, with risks that it could trigger a global food crisis.

Ukraine -- one of the world's largest grain producers -- will likely export only half the amount it did in the previous season, the Ukrainian Grain Association said.

The conflict was already translating into higher costs for essentials from cereals to sunflower oil to maize, with the poorest among the hardest hit.

The head of the African Union, Senegalese President Macky Sall, is to visit Russia on Friday for talks with Putin.

The visit is aimed at "freeing up stocks of cereals and fertilizers, the blockage of which particularly affects African countries", along with easing the Ukraine conflict, Sall's office said.

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© Agence France-Presse