Blast early on Saturday causes road bridge to collapse and engulfs rail bridge in flames

• Analysis: impact of bridge explosion will be felt all the way to the Kremlin

The parliamentary leader of President Volodymyr Zelenskiy’s party has stopped short of claiming that Kyiv was responsible for the Kerch bridge explosion but appeared to cast it as a consequence of Moscow’s takeover of Crimea and attempts to integrate the peninsula with the Russian mainland.

“Russian illegal construction is starting to fall apart and catch fire. The reason is simple: if you build something explosive, then sooner or later it will explode,” David Arakhamia, the leader of the Servant of the People party, wrote on Telegram.

Blasts rock Kharkiv as Zaporizhzhia hit with ‘kamikaze drones’; Zelenskiy warns on nuclear weapons; Moscow declares Russian rapper a ‘foreign agent’

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Kyiv’s troops advanced in southern Kherson province and made additional gains in east

• Russia-Ukraine war – live updates

Russia no longer has full control of any of the four provinces of Ukraine it says it annexed last week after Ukrainian troops advanced dozens of kilometres in Kherson province in the south of the country and made additional gains in the east.

On Monday, the Russian military acknowledged that Kyiv’s forces had broken through in the Kherson region. It said the Ukrainian army and its “superior tank units” had managed to “penetrate the depths of our defence” around the villages of Zoltaya Balka and Alexsandrovka.

Troops raise Ukrainian flag in city hours after Putin said area was Russia’s ‘for ever’, with Moscow admitting its forces have retreated

• Russia-Ukraine war – latest updates

Russia suffered a humiliating military defeat on Saturday when Ukrainian troops liberated the key eastern city of Lyman, with videos showing them raising a blue and yellow national flag and performing a victory dance.

In a severe embarrassment for Vladimir Putin, Russia’s ministry of defence admitted its soldiers had retreated. They had been “withdrawn to more advantageous lines”, the ministry said, after their encirclement by Ukrainian forces.

At least 25 people killed as Russian missiles hit civilian convoy; Vladimir Putin to formalise annexation of four occupied regions of Ukraine

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A civilian convoy of cars heading to pick up relatives trying to flee Russian occupied territory in Ukraine has been hit by Russian forces near the city of Zaporizhzhia, with initial reports saying at least 25 people were killed and 50 people injured. Footage posted on social media showed a horrific scene with dead and injured people lying on a road on the south-eastern outskirts of the city.

The governor of Zaporizhzhia region, Oleksandr Starukh, said in a statement: “The enemy launched an attack on a civilian convoy and the outskirts of the city. People were standing in line to leave for the occupied territory to pick up their relatives and to deliver aid. There are dead and wounded. Emergency services are at the site.

According to locals, 60 cars had gathered on a road in two lines after registering for a convoy that was due to take people back into the Russian-occupied territories in the south, some planning to return to homes in places such as Mariupol, others planning to fetch relatives and bring them to government-occupied territory for fear that Russia will prevent people from leaving. In the hours before the attack, Russia launched strikes on several cities, including the centre of the nearby city of Dnipro.

The attack on the convoy on Friday morning came amid a feared Russian escalation in its war in Ukraine, as the Russian president, Vladimir Putin, prepared to publicly sign annexation orders for four regions.

Putin will sign accession documents at the Kremlin before delivering a speech. A pop concert is also planned on Red Square, where a stage and screens have been set up. The territory Russia controls amounts to about 15% of Ukraine’s total area.

The Kremlin said again on Friday that it would consider attacks against any part of the regions of Ukraine that it is about to annex – Luhansk, Donetsk, Zaporizhzhia and Kherson – as acts of aggression against Russia itself.

Kremlin spokesman Dmitry Peskov told reporters Russia would “de jure” incorporate parts of Ukraine which are not under the control of Russian forces. Of the four regions, Luhansk and Kherson are the only territories that Russia is close to having total control over.

This live blog is now closed, you can find our latest coverage of the Russia-Ukraine war here

Sweden’s foreign minister Ann Linde has said on the public television broadcaster SVT this morning that the suspected sabotage against the Nord Stream gas pipelines does not constitute an attack on Sweden, Reuters reports.

If you missed it yesterday, my colleague Dan Sabbagh offered this analysis, suggesting that even if European nations decided that Russia had been behind the action, it was unlikely to generate a military response, since the suspected explosions were outside of Danish territorial waters, and technically on assets owned by Russia’s Gazprom.

This is Martin Belam taking over the live blog in London. You can reach me at martin.belam@theguardian.com

Volodymyr Zelenskiy vows to defend Ukrainian citizens after Moscow-backed officials declare victory in regional ‘referendums’ on joining Russia

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President Volodymyr Zelenskiy has said Ukraine will “defend” its citizens in Moscow-held regions that authorities have claimed voted in favour of merging with Russia. Zelenskiy said in a video on Telegram: “We will act to protect our people, both in the Kherson region, in the Zaporizhzhia region, in the Donbas, in the currently occupied areas of the Kharkiv region, and in the Crimea.” Agence France-Presse reported that Kremlin-backed officials in the four Ukrainian regions holding “referendums” claimed victory on Tuesday amid international condemnation of sham ballots.

Poland’s foreign minister, Zbigniew Rau, has said Nato’s response to any use of nuclear weapons in Ukraine should be non-nuclear but “devastating”. His comments come after Dmitry Medvedev, the hawkish deputy chairman of Russia’s security council, again threatened the west with the use of nuclear weapons in Ukraine, saying: “Imagine that Russia is forced to use the most formidable weapon against the Ukrainian regime, which has committed a large-scale act of aggression, which is dangerous for the very existence of our state. I believe that Nato will not directly intervene in the conflict, even in this situation.”

European leaders have said sabotage is the most likely cause of leaks in two Nord Stream gas pipelines between Russia and Europe, after seismologists reported explosions around the Baltic Sea lines. Denmark’s military issued an image of gas bubbling at the surface of the Baltic after the “unprecedented” damage to the pipelines.

The European Commission president, Ursula Von der Leyen, threatened the “strongest possible response” to any deliberate disruption of European energy infrastructure in the wake of the Nord Stream damage. Swedish police said they had launched a preliminary investigation into possible sabotage. Poland’s prime minister, Mateusz Morawiecki, has called the leaks “an act of sabotage” that “related to the next step of escalation of the situation in Ukraine”.

President Vladimir Putin is scheduled to address both houses of the Russian parliament on Friday and may use the address to formally announce the accession into Russia of the Ukraine territories that held referendums, the British Ministry of Defence said in its latest intelligence update. Putin said on Tuesday that Russia wanted to “save people” in the territories.

The US secretary of state, Antony Blinken, said the west would never recognise Russia’s annexation of Ukrainian territory, which he called part of a “diabolical scheme” by Moscow. Nato denounced the referendums as a “sham” and “violation of international law”.

The United Nations human rights office has said Russia’s invasion of Ukraine led to a wide range of human rights violations – including extrajudicial killings and torture – that could amount to war crimes, and had caused a dire rights situation. The Office of the High Commissioner for Human Rights said in a report that it was particularly concerned about torture and ill treatment of detainees by Russian forces and affiliated armed groups, but that there had been rights violations by both sides.

Georgia and Kazakhstan said that tens of thousands of Russians had flooded into their countries from neighbouring Russia as military-aged men avoid military call-up following Vladimir Putin’s mobilisation.

Moscow said it would not request the extradition of Russians travelling abroad to avoid being called-up to fight in Ukraine.