Ukrainian forces were still holding out in Sievierodonetsk on Tuesday, resisting Russia's all-out assault to capture a bombed-out wasteland that Moscow has made the principal objective of its invasion in recent days.

    Both sides said Russian forces now controlled between a third and half of the city. Russia's separatist proxies acknowledged that capturing it was taking longer than hoped, despite one of the biggest ground assaults of the war.

    "We can say already that a third of Sievierodonetsk is already under our control," Russia's TASS state news agency quoted Leonid Pasechnik, the leader of the pro-Moscow Luhansk People's Republic, as saying.

The Ukrainian head of the city administration, Oleksandr Stryuk, said the Russians now controlled half of the city.

    "Unfortunately ... the city has been split in half. But at the same time the city still defends itself. It is still Ukrainian," he said, advising those still trapped inside to stay in cellars.

    Thousands of residents remain trapped. Russian forces are advancing towards the city centre, but slowly, and have not succeeded in encircling the Ukrainian defenders holding out there.

    Regional governor Serhiy Gaidai told Ukrainian television there did not appear to be a risk of Ukrainian forces being encircled, though they could ultimately be forced to retreat across the Siverskiy Donets river to Lysychansk, the twin city on the opposite bank.

    Jan Egeland, secretary general of the Norwegian Refugee Council aid agency which had long operated out of Sievierodonetsk, said he was "horrified" by its destruction.

    "We fear that up to 12,000 civilians remain caught in crossfire in the city, without sufficient access to water, food, medicine or electricity. The near-constant bombardment is forcing civilians to seek refuge in bomb shelters and basements, with only few precious opportunities for those trying to escape."

OIL BAN

    After having failed to capture Kyiv, been driven out of northern Ukraine and made only limited progress elsewhere in the east, Moscow has concentrated the full force of its armed might in recent days on Sievierodonetsk, which had a pre-war population of around 110,000.

    But the huge battle has come at a massive cost, which some Western military experts say could hurt Russia's ability to fend off eventual Ukrainian counterattacks elsewhere, regardless of who wins the battle for Sievierodonetsk.

    "When the Battle of Severodonetsk ends, regardless of which side holds the city, the Russian offensive at the operational and strategic levels will likely have culminated, giving Ukraine the chance to restart its operational-level counteroffensives to push Russian forces back."

    The EU will now ban import of Russian oil by sea. Officials said that would halt two-thirds of Russia's oil exports to Europe at once, and 90% by the end of this year as Germany and Poland also phase out imports by pipeline.

    Ukraine says the sanctions are taking too long and are still too full of holes to stop Russia: "If you ask me, I would say far too slow, far too late and definitely not enough," said Ihor Zhovkva, deputy head of President Volodymyr Zelenskiy's office.