Russian forces appear to have made progress from north-east Ukraine in their slow fight to reach the capital Kyiv, while tanks and artillery pounded places already under siege with shelling so heavy it prevented residents of one city from burying the growing number of dead.
In Mariupol, unceasing barrages have thwarted repeated attempts to bring in food and water and to evacuate trapped civilians.
The Ukrainian government said Russian forces had shelled a mosque sheltering more than 80 people in the besieged city. There were no reports of any casualties.
The city’s death toll has passed 1,500 in 12 days of attack, the mayor’s office said, and a strike on a maternity hospital in the city of 446,000 this week killed three people.
Ukraine’s military said Russian forces have captured the eastern outskirts of Mariupol, but added that Russian Major General Andrei Kolesnikov had died in the fighting.
Russian forces have hit more than a dozen hospitals since they invaded Ukraine on February 24, according to the World Health Organisation.
Ukrainian officials reported on Saturday that heavy artillery had damaged a cancer hospital and several residential buildings in Mykolaiv, a city 300 miles west of Mariupol.
The hospital’s head doctor, Maksim Beznosenko, said several hundred patients were in the facility during the attack but no one was killed.
The invading Russian forces have struggled far more than expected against determined Ukrainian fighters, but Moscow’s stronger military threatens to grind down the defending forces, despite a flow of weapons and other assistance from the West for Ukraine’s westward-looking, democratically elected government.
The Kremlin’s forces appeared to be trying to regroup and regain momentum after encountering heavy losses and tough resistance over the past two weeks.
They were blockading Kharkiv, Ukraine’s second-largest city, even as efforts have been made to create new humanitarian corridors around it and other urban centres so aid can get in and residents can get out.
Ukraine’s emergency services reported on Saturday that the bodies of two women, a man and two children had been pulled from an apartment building struck by shelling in the city.
The Russians also stepped up attacks on Mykolaiv, 290 miles south of Kyiv, in an attempt to encircle the city.
In a multi-front attack on the capital, the Russians’ push from the north east appeared to be advancing, a US officials said. Combat units were moved up from the rear as the forces advanced to within 20 miles of Kyiv.
A daily intelligence update said elements of the large Russian military column north of Kyiv have dispersed. It said this is likely to support a Russian attempt to encircle the capital, and could also be an attempt by Russia to reduce its vulnerability to Ukrainian counter attacks, which have taken a significant toll on Russian forces.
New commercial satellite images appeared to capture artillery firing on residential areas that stood between the Russians and the capital. The images from Maxar Technologies showed muzzle flashes and smoke from big guns, as well as impact craters and burning homes in the town of Moschun, 20 miles from Kyiv, the company said.
On the economic and political front, the US and its allies moved to further isolate and sanction the Kremlin. President Joe Biden announced the US will dramatically downgrade its trade status with Russia and ban imports of Russian seafood, alcohol and diamonds.
The move to revoke Russia’s “most favoured nation” status was taken in co-ordination with the European Union and the G7.
“The free world is coming together to confront Putin,” Mr Biden said.
Ukrainian President Volodymyr Zelensky appeared on video to encourage his people to keep fighting.
“It’s impossible to say how many days we will still need to free our land, but it is possible to say that we will do it,” he said from Kyiv.
He said authorities were working on establishing 12 humanitarian corridors and trying to ensure food, medicine and other urgently needed basics get to people across the country.
He also accused Russia of kidnapping the mayor of one city, Melitopol, calling the abduction “a new stage of terror”.
The Biden administration had warned before the invasion of Russian plans to detain and kill targeted people in Ukraine.
The US also said Russia has launched nearly 810 missiles into Ukraine.
Until recently, Russia’s troops had made their biggest advances on cities in the east and south while struggling in the north and around Kyiv. They also have started targeting areas in western Ukraine, where large numbers of refugees have fled.
Russia said on Friday that it had used high-precision long-range weapons to put military air fields in the western cities of Lutsk and Ivano-Frankivsk “out of action”. The attack on Lutsk killed four Ukrainian servicemen, the mayor said.
Russian air strikes also for the first time targeted Dnipro, a major industrial hub in the east and Ukraine’s fourth-largest city, with about a million people. One person was killed, Ukrainian officials said.
International law prohibits the use of the bombs, which scatter smaller explosives over a wide area, in cities and towns.