Ukraine claims its forces are under intense Russian bombardment in Lysychansk's eastern city, but denies that they are being surrounded.
It is part of the industrial Donbas and the last Ukrainian-held Luhansk city. Russia took the city of Severodonetsk, which is nearby, last month.
Serhiy Haidai, Luhansk governor, stated that "we barely have the time to put out major fires in Lysychansk."
Russia also launched more missiles at cities to the south and north.
A series of attacks damaged the lines of electricity and railway tracks in Kharkiv's northern city. There were no casualties.
Multiple explosions shaken the southern city of Mykolaiv, which is on a crucial route to Odesa port.
Although the Russian defense ministry claimed that its air force had destroyed five command posts in Ukraine and several ammunition dumps with its bombs, this claim was not independently verified.
The explosions occurred one day after more than 20 Russians were killed in a missile attack on a block near Odesa.
On Saturday, Alexander Lukasenko, the President of Belarus, said that his country's air defenses had destroyed Ukrainian missiles. However he didn't specify where. He is an ally of Russia's Vladimir Putin, and allowed Russian troops from Belarus to invade Ukraine in February.
He said, "They are provoking me... Three days ago maybe a little more, an attempt was made to strike military facilities in Belarusian territory from the territory of Ukraine." "But, thank goodness, the Pantsir antiaircraft systems were able to intercept all of the missiles.
He said that he was not looking to fight in Ukraine.
Russia is concentrating its ground offensive on the Donbass, and Governor Haidai stated that artillery fire was hitting Lysychansk in several directions.
However, a spokesperson for the Ukraine National Guard denied claims made by Russian-backed Luhansk separatists to have encircled the city.
Russian sources tweeted video of the Soviet flag being displayed at Lysychansk's war memorial, but this has not been confirmed.
Russian-backed Luhansk separatists claimed that they had "occupied strategic heights last, which allows us confirm that Lysychansk has been completely encircled."
The UK Defence Ministry has released its latest intelligence update stating that Russian forces "continued to make minor advances around Lysychansk with air and artillery strike".
It accuses Russia also of using Soviet-era antiship missiles in a "secondary land attack role", which is not what they were intended for. According to the ministry, many civilians died in Odesa and Kremenchuk due to the Kh-22 and Kh-32 missiles.
Slovyansk was a key Donbas city that Ukrainian forces held. The Russians have also shelled it again. The mayor Vadym Lyakh claimed that four victims of banned Russian cluster munitions were killed there. This claim was also not confirmed by the BBC.
