Russian forces in eastern Ukraine are fortifying their defences and it will be hard for Kyiv’s troops to repeat the rapid success of their recent lightning counter offensive, a senior regional Ukrainian official warned yesterday.

Russian President Vladimir Putin on Wednesday told UN chief Antonio Guterres during a phone call that the "priority" should be to send Ukrainian grain to countries in greatest need, the Kremlin said.

Ukrainian President Volodymyr Zelensky yesterday promised “victory” on a visit to the strategic city of Izyum that was recently recaptured from Russia by Kyiv’s army in a lightning counter-offensive.

Armenia said yesterday that at least 49 soldiers had been killed in the worst clashes with Azerbaijan since their war two years ago, but Russia said it had convinced the historic rivals to agree to a rapid ceasefire.

Ukraine on Tuesday vowed to liberate all its territory after driving back Russian forces in the northeast of country and raising flags over battle-scarred towns, calling on the West to speed up deliveries of weapons to back the dramatic advance.

Ukrainian forces swept deeper into territory seized from fleeing Russian troops yesterday, as joyful residents returned to former frontline villages and Moscow grappled with the consequences of the collapse of its occupation force in northeastern Ukraine.

Ukraine said yesterday that its forces were pushing back Russia’s military from strategic holdouts in the east of the country after Moscow announced a retreat from Kyiv’s sweeping counter-offensive.

Moscow abandoned its main bastion in northeastern Ukraine yesterday, a sudden apparent collapse of one of the war’s principal front lines after Ukrainian forces moved to encircle the area in a shock advance.

Swiftly advancing Ukrainian troops were bearing down on the main railway supplying Russian forces in the east yesterday, after the collapse of a section of Russia’s front line caused the most dramatic shift in the war’s momentum since its early weeks.

Ukraine yesterday claimed a military breakthrough in its counter-offensive against Russian invaders as US Secretary of State Antony Blinken, on a surprise visit to Kyiv, unveiled another $2.8 billion in military aid.

Ukraine made its boldest claim yet of success on the battlefield in its week-old counter-offensive against Russian forces in the south, while European markets reopened yesterday in free-fall after Russia kept its main gas pipeline to Germany shut.

Ukrainian President Volodymyr Zelensky has told Europeans to expect a difficult winter as the Russian assault on his country leads to cuts in oil and gas exports by Moscow.

Stepping up an energy war between Russia and the West, Moscow has announced it will keep its main gas pipeline to Germany shut and G7 countries said they planned a price cap on Russian oil exports.

Russia has scrapped a Saturday deadline to resume gas flows via the Nord Stream 1 pipeline, one of the main supply routes to Europe, after saying it discovered a fault during maintenance, deepening Europe's difficulties in securing fuel for winter.

United Nations experts who crossed into Russian-held territory in Ukraine to assess the safety of Europe's biggest nuclear energy plant are seeking on Friday to assess physical damage to the facility, where both sides warn of possible disaster.

A team of UN experts yesterday arrived at Ukraine’s Zaporizhzhia atomic plant complex to assess the risk of a radiation disaster after being delayed several hours by shelling near the site.

UN nuclear inspectors set off for Ukraine’s Zaporizhzhia nuclear power plant yesterday after weeks of shelling nearby sparked fears of a Fukushima-style radiation disaster, with tensions rising between Kyiv and Moscow over the visit.

Ukrainian President Volodymyr Zelensky has urged Russian troops to flee for their lives after his forces launched an offensive to retake southern Ukraine, but Moscow said it had halted the attack in its tracks and inflicted heavy losses on Kyiv.

Ukraine yesterday announced the start of a long-awaited counter-offensive to retake territory in the south seized by Russian forces since their invasion six months ago, a move reflecting Kyiv’s growing confidence as Western military aid flows in.

Europe could face several winters of gas shortage as a result of the cuts to Russian supplies, Shell Chief Executive Ben van Beurden said.