Ukraine's military intelligence agency says Russia has so far turned over the bodies of 210 Ukrainian fighters killed in the battle for Mariupol. It says most were among the last holdouts in the Azovstal steelworks.
The agency did not specify Tuesday how many more bodies are believed to remain in the rubble of the plant.
Russia now controls the destroyed port city, and began turning over bodies last week. Ukraine said Saturday that the two sides had exchanged 320 bodies, with each getting back 160. It is unclear whether any more bodies have been given to Russia.
The Ukrainian fighters defended the steelworks for nearly three months before surrendering in May under relentless Russian attacks from the ground, sea and air.
Russia now claims to have taken control of 97 per cent of one of the two provinces that make up Ukraine's Donbas, bringing the Kremlin closer to its goal of fully capturing the eastern industrial heartland of coal mines and factories.
Russian Defence Minister Sergei Shoigu said Moscow's forces hold nearly all of Luhansk province. And it appears that Russia now occupies roughly half of Donetsk province, where Mariupol is located, according to Ukrainian officials and military analysts.
After abandoning its bungled attempt to storm Kyiv two months ago, Russia declared that taking the entire Donbas is its main objective. Moscow-backed separatists have been battling Ukrainian government forces in the Donbas since 2014, and the region has borne the brunt of the Russian onslaught in recent weeks.
Early in the war, Russian troops also took control of the entire Kherson region and a large part of the Zaporizhzhia region, both in the south. Russian officials and their local appointees have talked about plans for those regions to either declare their independence or be folded into Russia.
But in what may be the latest instance of anti-Russian sabotage inside Ukraine, Russian state media said Tuesday that an explosion at a café in the city of Kherson wounded four people. Tass called the apparent bombing in the Russian-occupied city a "terror act."
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Before the Feb. 24 invasion, Ukrainian officials said Russia controlled some 7 per cent of the country, including the Crimean Peninsula, which Russia annexed in 2014, and areas held by the separatists in Donetsk and Luhansk. Last week, Ukrainian President Volodymyr Zelensky said Russian forces hold 20 per cent of the country.
While Russia has superior firepower, the Ukrainian forces are entrenched and have shown the ability to counterattack.
Zelensky said Russian forces made no significant advances in the eastern Donbas region over the past day.
"The absolutely heroic defence of the Donbas continues," he said late Tuesday in his nightly video address.
Zelensky said the Russians clearly did not expect to meet so much resistance and are now trying to bring in additional troops and equipment. He said the same was true in the Kherson region.
Speaking earlier to a Financial Times conference, Zelenskyy insisted on Ukraine's need to defeat Russia on the battlefield but also said he is still open to peace talks with Russian President Vladimir Putin.
But a former senior U.S. intelligence officer said the time isn't right.
"You're not going to get to the negotiating table until neither side feels they have an advantage that they could push," said Andrea Kendall-Taylor of the Washington-based Center for a New American Security.
The Russians "think they will be able to take the whole of the Donbas and then might use that as the opportunity to call for negotiations," Kendall-Taylor said at an online seminar organized by Columbia and New York universities.
Shoigu, the Russian defence minister, said Moscow's forces have seized the residential quarters of Severodonetsk and are fighting to take control of an industrial zone on the city's outskirts and nearby towns.
Severodonetsk and nearby Lysychansk have seen heavy fighting in recent weeks. They are among a few cities and towns in the Luhansk region still holding out against the Russian invasion, which is being helped by local pro-Kremlin forces.
Shoigu added that Russian troops were pressing their offensive toward the town of Popasna and have taken control of Lyman and Sviatohirsk and 15 other towns in the region.
Ukrainian presidential adviser Mykhailo Podolyak urged his people not to be downhearted about the battlefield reverses.
"Don't let the news that we've ceded something scare you," he said in a video address. "It is clear that tactical manoeuvres are ongoing. We cede something, we take something back."
Luhansk Gov. Serhiy Haidai conceded that Russian forces control the industrial outskirts of Severodonetsk.
"The toughest street battles continue, with varying degrees of success," Haidai said. "The situation constantly changes, but the Ukrainians are repelling attacks."
Moscow's forces also kept up their artillery barrage of Lysychansk. Haidai said Russian troops shelled a market, a school and a college building, destroying the latter. At least three people were wounded, he said.
"A total destruction of the city is under way. Russian shelling has intensified significantly over the past 24 hours. Russians are using scorched-earth tactics," Haidai said.
Meanwhile, the U.S. military has begun training Ukrainian forces on the sophisticated multiple rocket launchers that the Biden administration agreed last week to provide. The Pentagon said the training is going on at a base in Germany and elsewhere in Europe.
The High Mobility Artillery Rocket System, or HIMARS, is mounted on a truck and can carry a container with six rockets, which can travel about 70 kilometres. Officials said it would take about three weeks of training before they could go to the battlefront.
The war also brought a standoff Tuesday between the head of the UN nuclear watchdog agency and Ukrainian authorities over the biggest nuclear power plant in Europe.