The situation "worsened" for Ukrainian forces in the eastern city of Sievierodonetsk, the regional governor said, after Ukraine had claimed advances, reported DW, quoting news agencies AFP, AP, dpa and Reuters.
Luhansk regional governor, Serhiy Gaidai, told Ukranian television that "the fiercest fighting is in Sievierodonetsk. Fast-moving fighting is happening right now," and that the situation for the Ukranian military had "worsened a bit" overnight.
Ukrainian forces have been trying to hold their ground after saying they had retaken half of the embattled city in Luhansk province, where Russian forces have concentrated their assault on Ukraine's eastern Donbas heartland.
DW correspondent Mathias Bölinger said that "the two armies are meeting each other in the streets. We had heard yesterday about some successes by the Ukrainians but it is very hard to confirm anything except that both armies are inside the city."
One aspect of the fighting that could be confirmed was that Sievierodonetsk is "a center of Ukranian Christian Orthodoxy and we’ve seen a very historic church burning."
Ukraine had said earlier that it regained control over "half" of the city.
Russian governor says border town hit by shelling
Roman Starovoit, governor of Kursk Oblast, claimed that the village of Tyotkino near the Ukrainian border came under fire early on Monday morning. He said that a few local businesses and a bridge had been hit.
The bridge is believed to have been a rail passageway used by the Russian military to ferry troops into Ukraine. Tyotkino has been hit several times in recent weeks, as Russian reports of attacks on its territory increase.
Meanwhile, early Sunday explosions were heard in the capital Kyiv and videos showing cruise missiles soaring above the capital appeared on social media.
Russia's Defense Ministry said tanks and other armored vehicles supplied to Ukraine by Eastern European countries had been destroyed by Russian forces in a barrage of missile strikes on the Ukrainian capital.
The ministry said high-precision, long-range air-launched missiles were used in the strikes on the outskirts of Kyiv, with T-72 tanks among the weaponry hit in the attacks. The damage was not immediately confirmed by Ukraine's military.
Ukraine's state nuclear power operator Energoatom did say though that one Russian cruise missile that was possibly aimed at the Ukrainian capital, Kyiv, flew over the South Ukraine Nuclear Plant at a dangerously low altitude.
In April 1986, Ukraine, then a Soviet republic, was the site of a major nuclear catastrophe when a reactor at the Chernobyl Nuclear Plant went into meltdown. The disaster is considered the worst-ever such incident in the world in terms of costs and casualties.
Russian President Vladimir Putin warned Russia will respond to the West delivering long-range missiles to Ukraine.
His remarks come after the US pledged to supply Kyiv with M142 systems armed with precisions-guided missiles. The range of the missiles, according to media reports, would be between 70 to 80 kilometers (43.5 to 50 miles).
Ukraine's Defense Minister Oleksiy Reznikov believes the war in Ukraine could end before the end of 2022.
His comments come a day after presidential adviser Mykhailo Podoliak also said it was hard to talk about deadlines for ending the war, but judging by the "stockpiled weapons, this could drag on for a period of two to six months."
In an intelligence update, the UK Ministry of Defense said counterattacks carried out by Ukrainian forces in the eastern city of Sievierodonetsk might be negating some of the advances made by attacking Russian troops.
Meanwhile, Ukrainian President Volodymyr Zelenskyy visited the Zaporizhzhia region and two towns near the front lines, Lysychansk and Soledar, he said in his nightly video address.
During his visit to Zaporizhzhia, he met with the head of the regional military administration, Oleksander Starukh, and national police in the region.
"I am proud of everybody I met, everyone I shook hands with, everyone with whom I connected with and had expressed my support," Zelenskyy said.
Starukh reportedly told Zelenskyy that nearly 60% of the territory in Zaporizhzhia region has been occupied by Russian troops as fighting continues. Seventy-seven villages in the region have seen their electricity cut, Starukh said.
Temporary shelters for those fleeing from nearby Kherson and Mariupol have also been set up. Zelenskyy urged local leaders to continue the flow of aid to those fleeing from elsewhere.