Russian forces "are exerting intense fire" as a multi-pronged offensive takes shape across three regions, according to the Ukrainian military leadership.
The General Staff of the Ukrainian Armed Forces said Thursday the Russians are focusing on trying to make a breakthrough in the Izium area of eastern Ukraine.
Izium — in the Kharkiv region — has become a staging ground for Russian forces as they try to advance through neighboring Donetsk and Luhansk regions.
"In order to strengthen the advancing group, the occupiers additionally moved airborne units to the city of Izium," the General Staff said in its daily operational update.
One of Russia's aims is to advance on the settlement of Lyman, which is near the industrial and transport hub of Sloviansk, it said.
"The enemy has improved its tactical position, trying to develop an offensive on the village of Lyman," the General Staff said, and is preparing to cross the Seversky Donets river.
Images emerged Wednesday showing a bridge over the river had been destroyed.
To the south-east, near Donetsk city, "the main efforts are focused on surrounding the Defense Forces," the General Staff said, with the towns of Mariinka and Ocheretyn under fire.
In the Luhansk region, the Russians are attacking the small town of Orikhove, the General Staff said.
Serhii Haidai, head of the Luhansk regional military administration, said Russia's offensive near Orikhove hasn't been successful. But the town of Lysychansk, about 28 kilometers (17 miles) away, was hit hard, with 13 buildings destroyed.
"All the hits in Lysychansk, 99% (...) are in residential districts, houses, markets and shops," Haidai said.
Haidai said the hospital at Severodonetsk was still working despite being shelled on Wednesday.
In southern Ukraine, according to the Ukrainian military, the Russians are using an airfield at Melitopol airfield as a base for Su-25 attack aircraft, Ka-52 attack helicopters and Mi-8 transport and combat aircraft.
The military acknowledged that the Russians have made incremental progress in the Kherson region as they try to advance toward the city of Mykolaiv. "The enemy has gained a foothold in the area of the settlement of Tavrijske," and from there is shelling nearby villages, it said.
The General Staff claimed that on Wednesday, one Russian plane and six drones were shot down, while on the ground five tanks and other armored vehicles had been destroyed.
Some background: As part of the second phase of its invasion, Russia has said it wants to secure all of Ukraine's eastern regions of Donetsk and Luhansk — parts of which Russian-backed separatists have controlled since 2014 — and to consolidate a land bridge linking the Russian region of Rostov with Crimea, which Russia seized from Ukraine eight years ago.