Russian President Vladimir Putin claims that Ukraine's counter-offensive has been unsuccessful, with its army suffering major losses. Speaking at a meeting of war correspondents, he said that Kyiv's losses were approaching a "catastrophic" level. That has not been verified, and Ukrainian President Zelensky has denied the counter-offensive is failing. "There is movement forward," he said in his nightly video address. He thanked Ukrainian troops for "every step and every meter of Ukrainian land that is being liberated from Russian evil". This was echoed by Valery Zaluzhny, the commander-in-chief of the country's armed forces, who wrote on Telegram there had been "some successes, we are implementing our plans, moving forward". Kyiv's counter-offensive is in its early stages, and modest gains have been made in the eastern Donetsk and south-eastern Zaporizhzhia regions. Zelensky has also claimed advances in Bakhmut. But the situation is not as clear-cut as the triumphant claims of liberation which came from Kyiv earlier this week. On Tuesday the BBC was granted access to some of the first settlements in eastern Donetsk where the Ukrainian flag is now flying. Many are deserted, and in some areas, Russian forces are pushing back. Nato chief Jens Stoltenberg said that while it was still "early days", progress was being made in repelling Russian troops. "What we do know is that the more land that Ukrainians are able to liberate, the stronger hand they will have at the negotiating table," he told US President Joe Biden at a White House meeting. Without providing evidence, Putin said the Ukrainians had lost over 160 tanks while Russia had lost 54. He also suggested Ukraine's troop losses were ten times greater than Russia's -- insisting Kyiv had not succeeded "in any of the sectors". His comments were dismissed by a US official, who anonymously told the AP news agency they were "not accurate" and warned against taking Moscow's public assessments seriously. Although most of Putin's statements during his meeting with war correspondents were typically self-congratulatory, he did acknowledge that authorities in Moscow could have better anticipated recent cross-border attacks into Russia from Ukraine. Putin also suggested that Russia was short of "high-precision ammunition, communications equipment, aircraft, drones, and so on" - despite weapon production having increased over the past year. Ukraine has had longstanding concerns about Russia's ability to build weaponry. On Tuesday, Zelensky again called for tougher sanctions to halt the flow of weapon components, some of which he said were being manufactured by Ukraine's partner countries. He said that Russia was using such components to build the type of missiles that on Tuesday struck an apartment building and warehouses in Kryvyi Rih, killing 11 people and wounding dozens more. On the same day, the US announced it would send a new military aid package to Ukraine worth $325 million. Separately, Belarusian leader Alexander Lukashenko suggested his country was receiving nuclear weapons from Russia that were "three times more powerful" than the atomic bombs used in Hiroshima and Nagasaki. He did not say whether they had already received the weapons or not, but claimed their deployment to Minsk was necessary to deter potential aggression. Earlier this month, Russia said it would deploy tactical nuclear weapons on Belarusian soil from July -- seen as a warning to the West, which was increasing its military support for Ukraine. — BBC