Russia on Saturday claimed a new territorial victory over Ukrainian forces struggling to find weapons and troops while the two sides staged deadly new aerial attacks on each other.
As a militant attack on a Moscow concert hall became a new flashpoint dispute between the arch-rivals, Russia's armed forces said they had seized the Ukrainian village of Ivanivske, just west of Bakhmut, the devastated city seized 10 months ago.
Russian forces have taken control of a string of frontline settlements in recent weeks, as Ukrainian forces suffer troop and ammunition shortages.
The capture last month of Adviivka, near the Russian-held stronghold of Donetsk, was the first major territorial gain made by Russia since Bakhmut and was hailed by President Vladimir Putin as a sign that Russian forces are back on the offensive.
Russia's defence ministry said in a statement that the army had "liberated" Ivanivske, which is also close to the town of Chasiv Yar that could become the next target.
If Russia took Chasiv Yar, it could step up attacks on the strategic city of Kramatorsk that is already facing growing bombardment.
The Russian claim came amid mounting tensions over an attack on a Moscow concert hall on Friday that authorities said left at least 133 dead.
President Vladimir Putin said in a nationally televised speech on Saturday that the four detained "perpetrators" were "travelling towards Ukraine where, according to preliminary information, they had a window to cross the border".
Russia's FSB security service said earlier that the assailants had been "in contact" with people in Ukraine as they tried to flee the country.
Ukraine has strongly denied any involvement, saying that Russia was looking for excuses to step up the war. The United States has said it has seen no sign of Ukrainian involvement in the Crocus City Hall attack.
While Ukraine has struggled to find weapons and soldiers for its war, it has kept up drone attacks on Russia, which has also launched increasing air assaults.
Multiple air attacks on the Russian border region of Belgorod adjoining Ukraine killed two people and injured at least seven, the regional governor said.
Further east, a drone attack on the Samara region caused a fire at a major oil refinery, the latest in a series of strikes against Russia's energy industry.
Belgorod governor Vyacheslav Gladkov wrote on Telegram that two districts in his region as well as the regional capital, Belgorod, had been hit in drone and air attacks. "It's shaping up to be a difficult morning," Gladkov said.
"As a result of an air attack by Ukrainian armed forces on Belgorod, three balconies collapsed in an apartment building. One of these apartments was occupied by a married couple. To much grief, the man died from his injuries on the spot," he said.
Ukraine said 34 Russian drone strikes had targeted its territory but 31 had been shot down. In the major city of Kharkiv, near the war frontlines, four people were hit by a Shahed drone.
Kharkiv, Ukraine's second city, was plunged into darkness on Friday after mass attacks on Ukraine's electricity supply and some 275,000 people in the city were still without power on Saturday, according to its governor Oleg Synegubov.
The blackout meant there was no water nor heating for much of the city, residents said.
