Heavy fighting is continuing at the besieged steel plant in Mariupol as Russian forces attempt to complete the capture of the strategically vital port.
The bloody battle comes amid growing suspicions that Russian President Vladimir Putin wants to present the Russian people with a major battlefield success in time for Victory Day on Monday.
It is the biggest patriotic holiday on the Russian calendar, marking the Soviet Union’s triumph over Nazi Germany.
Russians may be using ‘banned’ thermobaric bombs – follow latest updates
Some have also suggested Mr Putin could use the celebrations to expand what he calls the “special military operation”.
A declaration of all-out war would allow the Russian leader to introduce martial law and mobilise reservists to make up for significant troop losses.
The Kremlin has dismissed the speculation.
Denys Prokopenko, commander of the Ukrainian Azov regiment, has said “heavy, bloody battles” are underway at the sprawling site which has a network of underground tunnels.
“The situation is extremely difficult, but in spite of everything, we continue to carry out the order to hold the defence,” he added.
The Kremlin denied that there is any ground assault.
It is unclear how many Ukrainian fighters are inside, but Russia has said there are around 2,000 with 500 reported to be wounded.
An estimated 200 civilians are still holed up in the steel plant’s network of underground bunkers.
Civilians including women and children will need to be dug out from the bunkers by hand as Russian forces storm the site, Ukrainian President Volodymyr Zelenskyy has said.
“It will take time simply to lift people out of those basements, out of those underground shelters. In the present conditions, we cannot use heavy equipment to clear the rubble away. It all has to be done by hand.”
Other key developments
• Oil prices jumped following the proposed EU ban on Russian oil imports
• US President Biden said he would speak with leaders from the G7 advanced economies this week about more sanctions on Russia
• The US has provided intelligence that has helped Ukrainian forces kill around 12 Russian generals, the New York Times reports
• The armed forces of Ukraine’s neighbour Belarus began sudden large-scale drills to test their combat readiness.
Moscow struggling to gain momentum
It comes after the Red Cross said more than 300 civilians were evacuated from Mariupol and other nearby communities on Wednesday.
This includes “several dozen civilians” who left the besieged steel plant and reached Zaporizhzhia during a five-day safe passage operation, the charity said in a statement.
After 10 weeks of war, Ukraine’s military said it has recaptured some areas in the south and repelled other attacks in the east, further frustrating Mr Putin’s ambitions.
Ukrainian and Russian forces are fighting village by village as Moscow struggles to gain momentum in the eastern industrial heartland of the Donbas.
Russian forces shelled elsewhere in the Donbas and also kept up their bombardment of railway stations and other supply-line targets across the country – part of an effort to disrupt the supply of western arms, which have been critical to Ukraine’s defence.
Ukrainian forces said on Thursday they made some gains on the border of the southern regions of Kherson and Mykolaiv and repelled 11 Russian attacks in the Donetsk and Luhansk regions that make up the Donbas.
Russian forces struggling to gain traction
Five people were killed and at least 25 hurt in shelling of cities in the Donbas over the past 24 hours, Ukrainian officials said.
The attacks also damaged houses and a school.
It comes a day after Russian attacks were reported near Kyiv, in Cherkasy and Dnipro in central Ukraine, and in Zaporizhzhia in the south east.
An assessment by the Washington-based Institute for the Study of War said Russian forces are struggling to gain traction.
“Ukrainian defences have largely stalled Russian advances in eastern Ukraine,” it said on Wednesday.
“Russian forces intensified airstrikes against transportation infrastructure in western Ukraine (on Wednesday) but remain unable to interdict Western aid shipments to Ukraine,” it added.
Earlier British Prime Minister Boris Johnson spoke to Mr Zelenskyy and discussed the possible supply of longer-range weaponry.
Meanwhile, the UK’s Ministry of Defence said Belarusian forces have begun military exercises which will seek to hold Ukrainian forces back from fighting to protect the Donbas region.
The ministry said in an update: “Russia will likely seek to inflate the threat posed to Ukraine by these exercises in order to fix Ukrainian forces in the north, preventing them from being committed to the battle for Donbas.”