A Defence spokesman of Ukraine said hundreds of Russian troops are likely to have been killed in the incident.
Ukraine’s border guard agency also said the Russian military attacked the country from neighbouring Belarus.
The agency said the Russian troops unleashed an artillery barrage as part of an attack backed by Belarus.
“Attacks on border units, border detachments and checkpoints are carried out with the use of artillery, heavy equipment and small arms. The work of enemy sabotage and reconnaissance groups is also recorded,” ,” the agency said in a statement.
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The statement was issued as a Ukrainian interior ministry official reported the fall of the previously government-held town of Shchastya, on the eastern frontline with a rebel-held enclave.
Russian airstrikes reportedly hit an apartment complex in south of Kharkiv, Ukraine.