Ukraine's ground forces commander said on Monday Kyiv was planning its next move after Moscow shifted the focus of its offensive from a flagging assault on the eastern city of Bakhmut to another town further south, described as post-apocalyptic.
The Ukrainian military aims to wear down Russian forces as much as possible before launching a counteroffensive in the coming weeks or months - seeking to end the all-out invasion launched by Russian President Vladimir Putin 13 months ago.
Ukrainian ground forces commander Colonel General Oleksandr Syrskyi, who said last week that the counterattack could come "very soon", visited front line troops in the east on Monday and said his forces were still repelling Russian attacks on Bakhmut.
Defending the small city in the industrialised Donbas region that Russia has tried to seize for months was a "military necessity", he said, praising Ukrainian resilience in "extremely difficult conditions".
"We are calculating all possible options for the development of events, and will react adequately to the current situation".
Commander-in-Chief General Valery Zaluzhniy said on Saturday the situation was being "stabilised" around Bakhmut, where Russian forces say they are fighting street by street.
Last week, the Ukrainian military warned that Avdiivka, a smaller town 90 km (55 miles) further south, could become a "second Bakhmut" as Russia turns its attention there. Both towns have been reduced to rubble in fighting that both sides have called a "meat grinder".
"I am sad to say this, but Avdiivka is becoming more and more like a place from post-apocalyptic movies," said Vitaliy Barabash, head of the city's military administration. Only around 2,000 of a pre-war population of 30,000 remain and he urged them to leave.
A Ukrainian military video showed smoke billowing from ruined apartment blocks and dead soldiers on open ground and in trenches in Bakhmut.
Two people were killed and 29 wounded on Monday after Russian forces fired two S-300 missiles at the eastern city of Sloviansk northwest of Bakhmut, according to regional governor Pavlo Kyrylenko. President Volodymyr Zelenskiy posted a video of smouldering debris and vowed that "Ukraine will not forgive" such attacks. Moscow denies targeting civilians.
Inside Russia, the defence ministry said it had downed a Ukrainian drone on Sunday, adding three people were injured and apartment blocks were damaged in the attack south of Moscow.
Kyiv does not generally comment on reports of attacks inside Russia. The latest reported attack, on the town of Kireyevsk, in Tula region 220 km (140 miles) south of Moscow, appeared to be one of the closest yet to the Russian capital.
NUCLEAR DEPLOYMENT PLAN
As the invasion Putin launched to "demilitarise" Ukraine has flagged, he and other top Russian officials have played up the prospect the war could escalate to involve nuclear weapons: on Saturday he said he had struck a deal to station tactical nuclear weapons in neighbouring Belarus.
The Belarus plan, while not unexpected, is one of Russia's most pronounced nuclear signals yet and a warning to NATO over its military support for Ukraine, which has called for a meeting of the U.N. Security Council in response.
"Russia's nuclear rhetoric is dangerous and irresponsible," NATO spokeswoman Oana Lungescu said on Sunday.
"NATO is vigilant and we are closely monitoring the situation. We have not seen any changes in Russia's nuclear posture that would lead us to adjust our own."
Putin likened his Belarus plan to the United States stationing its weapons in Europe, insisting that Russia would not violate its nuclear non-proliferation promises.
However, Lungescu said Putin's non-proliferation pledge and his description of U.S. weapons deployment overseas were way off the mark.
"Russia's reference to NATO's nuclear sharing is totally misleading. NATO allies act with full respect of their international commitments," she added in a statement.
"Russia has consistently broken its arms control commitments."
Ukraine's security chief, Oleksiy Danilov, said Russia's plan would destabilise Belarus, which he said had been taken "hostage" by Moscow.
Others condemning Putin's plan included Lithuania, which said it would call for new sanctions against Moscow and Minsk, while EU policy chief Josep Borrell urged Belarus not to host the weapons and threatened more sanctions.
Belarus and Russia have close military ties, and Minsk allowed Moscow to use its territory as a staging point for the latter's invasion of Ukraine last year.
Experts see Russia's move as significant since it had been proud, until now, of not having deployed nuclear weapons outside its borders, unlike the United States. This may be the first time since the mid-1990s that it plans to do so.
The United States played down concerns about Russia's planned deployment.
"I can tell you we've seen nothing that would indicate Mr. Putin is preparing to use tactical nuclear weapons in any way whatsoever in Ukraine," White House National Security Council spokesman John Kirby told broadcaster CBC on Sunday.
"And I can also tell you that we haven't seen anything that would cause us to change our own strategic nuclear deterrent posture."
Tactical nuclear weapons are those used to make specific gains on a battlefield, rather than those capable of wiping out cities. It is unclear how many such weapons Russia has, since the topic is still shrouded in Cold War secrecy.
Putin asserted on Sunday that Western powers were building a new "axis" similar to the partnership between Germany and Japan during World War Two, while denying Russia was building a military alliance with China.
That was the reprise of a theme that has figured in his portrayal of the war as Moscow's fight against a Ukraine in the grip of supposed Nazis, abetted by Western powers menacing Russia. Ukraine rejects these as spurious pretexts for a war of imperial conquest.
(Reporting by Dan Peleschuk and Reuters bureaus Writing by Himani Sarkar and Philippa Fletcher Editing by Gerry Doyle, Clarence Fernandez, Peter Graff)