"[In] the Kharkiv region - we are stabilising the situation, holding our positions. Firmly. So strongly that the occupiers are palpably panicking," said Zelenskyy.
Ukrainian forces have recaptured a village close to the eastern city of Lysychansk, in a small but symbolic victory that means Russia no longer has full control of the Luhansk region.
Moscow has denounced fresh strikes in eastern Ukraine against areas they previously controlled, such as Donetsk where Russia-backed authorities claimed that 13 people were killed.
"[In] the Kharkiv region - we are stabilising the situation, holding our positions. Firmly. So strongly that the occupiers are palpably panicking," Ukraine's president, Volodymyr Zelenskyy, said during his nightly address.
Zelenskyy praised the momentum of Ukraine's counter-attack and warned that Russian troops faced an ultimatum -- surrender or escape.
Calls for referendums in Donbas
On Monday, civic chambers in the self-proclaimed republics of Luhansk and Donetsk called on the Russia-backed heads of their regions to hold referendums on joining Russia.
The Russia-installed head of the Donetsk region Denis Pushilin also published a video on his Telegram channel showing him speaking on the phone with his counterpart in Luhansk, Leonid Pasechnik.
Pushilin proposed to unite the efforts of their administrations in order to start preparations for referendums.
Andrei Turchak, the leader of United Russia, the main Kremlin-directed party, suggested that referendums in the Donbas and other Russia-controlled areas in Ukraine could be held on November 4 when Russia marks the National Unity Day.
Mykolayiv nuclear plant
Meanwhile, Kyiv claims Russian forces have carried out a missile strike that narrowly missed the Pivdennoukrainsk nuclear power plant in the Mykolayiv region, about 200km north of the conflict's southern frontline.
Ukraine’s state nuclear power company, Energoatom, said three reactors at the plant continued to operate and nobody was injured. It added that about 100 windows at the site were shattered and a brief power outage had occurred.