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Russia is moving troops and weapons towards the eastern Ukrainian city of Izium and using it as a focal point in their attempt to capture the Donbas region, Ukraine and the UK have said.
Ukraine said Russia suffered losses in an offensive near the city but was reinforcing its attack with a battery of Tulip mortar weapons and Tornado multiple rocket launchers moved from the Russian border region of Belgorod.
Britain, meanwhile, said Moscow sent 22 battalion tactical groups – a type of formation kept at high readiness by Russian military chiefs – near Izium as part of its attempt to advance along the "northern axis" of the Donbas.
Although Russia has struggled to gain momentum in the east, it is "highly likely" that it intends to proceed beyond Izium and capture the cities of Kramatorsk and Severodonetsk, the UK Defence Ministry said in a regular intelligence update.
"Capturing these locations would consolidate Russian military control of the north-eastern Donbas and provide a staging point for their efforts to cut off Ukrainian forces in the region," it said.
Russia said it shot down at least one Ukrainian drone near Izium and foiled the delivery of western arms to the Donbas by destroying six railway substations.
Those attacks included missile strikes in Lviv in western Ukraine, which has largely been spared the worst of the fighting. City Mayor Andriy Sadovyi said two people were injured and water and electricity supplies disrupted by the strikes.
At least 156 people have been evacuated from a steel plant in Mariupol, the scene of some of the heaviest fighting, Ukraine said. They were taken to the south-eastern city of Zaporizhzhia.
"This is not a victory yet, but this is already a result. I believe that there is a chance to save our other people," said Ukrainian President Volodymyr Zelenskyy.
He said Russia was flouting the terms of a ceasefire by continuing attacks on the Azovstal plant, where Moscow says Ukrainian fighters and mercenaries have taken shelter.
He taunted Moscow in an overnight address by saying the latest missile strikes were a sign that Russian generals "are trying to vent their powerlessness ... because they can't beat Ukraine".
Russia has reorganised its invasion around the Donbas after failing to capture Kyiv in the early weeks of its war. Western officials say the Russian military has been plagued by problems such as low morale, poor communication and misfiring equipment.
To the north, Russia's ally Belarus, which borders Ukraine, launched what it said were surprise military exercises on Wednesday to test the readiness of its army.
Military units tested their ability to "go on the alert, move to predetermined zones and undertake combat training", said the Defence Ministry in Belarus, which is accused by Ukraine and its allies of acting as a staging post for the Russian invasion.