Russian forces have launched rocket attacks that killed “dozens” of civilians in Ukraine’s second city, and began a renewed assault on the capital Kyiv, as Moscow faced unprecedented western sanctions and isolation.

Widespread use of indiscriminate weapons such as multiple rocket launchers against civilian areas, as used on Monday in the city of Kharkiv, suggested that the Kremlin, having failed to land a knockout blow in the first days of the war, was prepared to unleash more desperate methods.

The prosecutor of the international criminal court said he would launch an investigation into possible war crimes or crimes against humanity in Ukraine.

Late on Monday, the Ukrainian ambassador to the US accused Russian forces of using a thermobaric weapons, which use oxygen from the surrounding air to generate a high-temperature explosion.

“The devastation that Russia is trying to inflict on Ukraine is large,” said Oksana Markarova.

Satellite photos showed long Russian columns heading towards Kyiv. The satellite imaging company Maxar published a picture of a 40-mile convoy of forces about 30 miles from the capital. Inside Kyiv, air raid sirens sounded as evening fell and several detonations were reported.

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According to TheGuardian, blasts were also heard in Mariupol on the coast of the Sea of Azov. However, Russian forces have yet to take any major Ukrainian city.

Turkey said it would ban all warships from crossing the Bosphorus and Dardanelles straits leading to the Black Sea, blocking the route for at least four Russian vessels which are waiting to cross from the Mediterranean.

The Élysée Palace said after a call between Emmanuel Macron and Vladimir Putin that the Russian president had said he was “willing to commit” to ending attacks on civilians and civil infrastructure while ceasefire talks were taking place between Russian and Ukrainian officials in Belarus.

But on the fifth day of fighting and with Russian forces advancing more slowly than many analysts had expected, the Ukrainian interior ministry adviser Anton Herashchenko said on Monday Kharkiv had been “massively fired on”, leaving “dozens of dead and hundreds of wounded”.

After a classified briefing from US intelligence in Washington, Senator Chris Murphy said on Twitter: “The ability to keep supply lines running to Ukraine remains alive, but Russia will try to encircle and cut off Kiev in the next several weeks. The fight for Kiev will be long and bloody and Ukrainians are rapidly preparing for street to street combat.”

The talks between Russian and Ukrainian delegations near the Belarus-Ukraine border ended inconclusively, with national news agencies quoting officials as saying the negotiators would return to their respective capitals for consultations before embarking on a second round of talks in the coming days.

The Star