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 They had been “withdrawn to more advantageous lines”, the ministry said, after their encirclement by Ukrainian forces.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.

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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