As Thursday draws to a close in Kyiv and in Moscow, here are the key developments of the day:

Russian forces control most of the city of Sievierodonetsk in eastern Ukraine, with Ukrainians holding ground in its industrial zone, the governor of Luhansk said on social media. Ukrainian President Volodymyr Zelenskyy described the battle as the epicenter and key to the fate of the Donbas region. Both sides are believed to be suffering heavy losses in the urban fighting but are keeping casualty figures quiet. Western intelligence agencies say that a Russian victory in Sievierodonetsk would allow Russia to continue pushing farther into parts of eastern Ukraine.

Radiation detectors at the defunct Chernobyl nuclear power plant are back online. The International Atomic Energy Agency says the detectors have found normal radiation levels at Chernobyl, the site of one of the world's worst nuclear disasters in 1986. Russia seized the plant on the first day of its invasion in February. Russia's actions in the area raised international concerns they could cause radiation to spike in the exclusion zone around the plant. Ukraine retook control of the area in late March.

Two British citizens and a Moroccan received death sentences for fighting for Ukraine, in a court in the pro-Russian separatist Donetsk region. Russia's RIA Novosti reported that Aiden Aslin and Shaun Pinner of the United Kingdom and Saaudun Brahim from Morocco are accused of being mercenaries, who surrendered in Mariupol, Ukraine, in April. They have a month to appeal the sentence, the state news agency said. The British foreign secretary condemned the ruling as "a sham judgement with absolutely no legitimacy."

A Ukrainian court upheld a ban on a political party with ties to Russia. President Volodymyr Zelenskyy signed a law last month banning pro-Russian parties from government. The law allows the justice ministry to seize the assets of any party that "glorifies or justifies any armed aggression" against Ukraine. Before Russia's invasion, the only pro-Russian party in parliament held about one-tenth of seats. After the invasion, the party disbanded, rebranded and came back with an anti-war stance. But officials ordered the party to liquidate. Now there's no official pro-Russian position in Ukraine's government for the first time since independence 30 years ago.

At least 4.8 million refugees from Ukraine are in Europe, according to the United Nations refugee agency, UNHCR. The updated figure is based on data from national authorities and reflects Ukrainians' movements into different countries, as well as those returning home, since the Russian invasion. As of Tuesday, the agency recorded 7.3 million border crossings from Ukraine and another 2.3 million crossings back into the country.