"The invaders are assaulting Lysychansk oil refinery, holding north-western and south-eastern parts of the facility,” said Hayday.
“The enemy seeks to encircle Ukrainian troops, advancing towards Lysychansk from south and west.”
Local residents are spending almost all day in bomb shelters and cellars, according to the official.
“The city is under very dense artillery fire,” Hayday added.
“Numerous fires across residential buildings and infrastructure. Besides housing, two shopping malls are ablaze, with one of them having lost three floors to the fires. The other fire, raging across 500 square meters of area, was extinguished.”
Russia is still struggling to seize the Bakhmut highway – a key supply route to Lysychansk.
Ukraine’s General Staff warned that Russian troops are attempting to wrestle over control of Lysychansk-Bakhmut highway and blockade the city.