kyiv said on Thursday that it had recaptured some 700 km2 in this region of northeastern Ukraine in recent days, in particular the city of Balakliïa, as well as around twenty localities.
US Secretary of State Antony Blinken said from Brussels that Moscow's deployment of reinforcements shows that Russia is paying "a huge price".
The Russian Defense Ministry, which did not comment on the subject, nevertheless announced to Russian news agencies the deployment of reinforcements in this direction, broadcasting a video showing armored vehicles, howitzers and trucks driving in large numbers on roads not geolocated. It did not issue a statement detailing or commenting on these deployments.
A senior official of the occupation administration set up by Moscow in areas controlled by the Russian army, Vitali Gantchev, told Russian television channel Rossiya 24 on Friday that "fierce fighting" was underway around the town of Balakliïa, which kyiv said on Thursday it had reconquered.
"We no longer control Balakliya. Attempts to dislodge Ukrainian forces are underway, but the fighting there is fierce and our troops are held up on the outskirts" of the town, he said.
According to him, heavy fighting is also taking place near the town of Shevchenkové, still in the Kharkiv region. "There too, the Ukrainian armed forces are trying to break through the defenses. Reserves from Russia have been sent there, our troops are fighting back," said Vitali Gantchev.
The road from Kharkiv towards the southeast, towards Balakliïa, was open to traffic on Friday morning, noted an AFP team, an area that the Ukrainian army seems to have reconquered during fighting in recent days.
Many civilian cars were circulating, as well as military vehicles. Queues were also visible at several checkpoints.
Kharkiv, capital of the region of the same name and second city of Ukraine, is located in the northeast of the country, just on the border with Russia, and resists since the beginning of the invasion of February 24 Russian efforts to conquer her.
In addition to the breakthrough in this region, kyiv also claimed Thursday a series of successes in the South and East, claiming to have taken over territories and many localities.
If consolidated, these recent Ukrainian gains, together with those claimed in the south and east, are the most significant for Ukraine since the withdrawal of Russian troops from around kyiv in late March.
In the Donbass, a mining basin in eastern Ukraine where the heaviest fighting of the war has taken place in recent months, kyiv said on Thursday it had advanced two to three kilometers near Kramatorsk and Sloviansk and recaptured the village of Ozerne.
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45 km away, in Bakhmout, eight civilians were killed Thursday and 17 others injured in Russian strikes, according to Ukrainian authorities.
"Twenty houses, six buildings, four shops, the House of Culture and the administrative center of the city were damaged" in these Russian strikes, regional governor Pavlo Kyrylenko said on Friday, adding that the market had been "under the fire" from the Russian artillery.
Bakhmout, which had 70,000 inhabitants before the start of the conflict in late February, has no water or electricity for the fourth consecutive day, according to Mr. Kyrylenko.
Traveling to Prague, Lloyd Austin, US Secretary of Defense, hailed Ukraine's recent successes, noting that Western weaponry, such as US HIMARS, could be employed to "change the dynamics on the battlefield ". "We are seeing success in Kherson (south) now, success in Kharkiv, and so it's all very, very encouraging," he said.
US Secretary of State Antony Blinken was in Brussels for a meeting with NATO, where he intends to insist on the "unity" of the members of the organization to "ensure that our Alliance is as strong as possible to deter Russia from further aggression".