The ministry said its forces had “advanced deeply into the enemy defences”.
The Ukrainian army’s top commander said the situation was “complicated” but his forces were managing to hold back further Russian advances.
“All areas of the northern border are under enemy fire almost around the clock. The situation is difficult,” Kharkiv regional governor Oleg Synegubov said.
“The number of settlements where active hostilities are ongoing has increased,” he said.
Local prosecutors said four civilians had been killed in the offensive.
At an evacuation point near the front line in the Kharkiv region, AFP reporters on Sunday saw groups of people who had been evacuated from around the town of Vovchansk, most of them elderly and disoriented.
“We weren’t going to leave. Home is home,” said 72-year-old Lyuda Zelenskaya, hugging a trembling cat named Zhora.
Liuba Konovalova, 70 said she had endured a “really terrifying” night before her evacuation.
Volunteers assisted evacuees to a few wooden benches where they registered and received food before being evacuated towards Kharkiv, the regional capital.
Emergency services said more than 4,500 people had been evacuated from the Kharkiv region.
Oleksiy Kharkivsky, a senior police officer from Vovchansk helping to coordinate evacuations there, said it was “constantly under fire”.
“Everything in the city is being destroyed… You hear constant explosions, artillery, mortars. The enemy is hitting the city with everything they have,” he said.
He said evacuation teams had come under fire “many times”, estimating that around 1,500 people had been evacuated.
Synegubov estimated there were still around 500 civilians left in Vovchansk.
Volodymyr Tymoshko, head of police in the Kharkiv region, said Vovchansk was being attacked on three sides and Russian troops were on the outskirts.
Also Read: Russia attempts ground offensive into Ukraine’s Kharkiv
“Despite active fighting, the police are still taking out people who live some 300, 500 metres from the contact line at the moment,” he told AFP at the evacuation point.
The Ukrainian army said its defences were holding.
“Russian occupants’ attempts to break through our defence have been stopped,” Ukraine’s commander-in-chief Oleksandr Syrsky said on social media.
He said the situation in the Kharkiv region had “deteriorated significantly” and was “complicated”.
Ukrainian forces “are doing everything they can to hold their defensive lines and positions and inflict damage on the enemy,” he said.
‘Return the initiative to Ukraine’
Meanwhile, Russia said at least 20 people were injured in a Ukrainian missile strike on the border city of Belgorod which caused the partial collapse of a building.
Officials were quoted by Russian news agencies as saying that 12 people, including two children, were rescued from the rubble of the building.
Belgorod lies just across the border from Kharkiv.
In Kharkiv itself, mayor Igor Terekhov was quoted by the city council as saying there was no reason for people to leave the city despite the offensive.
“Despite all the events that are taking place in the region, Kharkiv is calm. We do not see people leaving,” he was quoted as saying.
On Saturday, AFP saw groups of people fleeing the border area arriving in vans and cars loaded with bags at a reception centre for evacuees near Kharkiv.
Evacuees — most of them elderly — received food and medical assistance.
President Volodymyr Zelensky said on Saturday that Ukrainian troops had been carrying out counterattacks in the border villages.
“Disrupting Russian offensive plans is now our number one task,” he said.
Troops must “return the initiative to Ukraine”, the president insisted, again urging allies to speed up arms deliveries.
Ukrainian officials had warned for weeks that Moscow might try to attack its northeastern border regions, pressing its advantage as Ukraine struggles with delays in Western aid and manpower shortages.
By Agencies.