The head of the European Union's executive Commission, Ursula von der Leyen, has spoken of her outrage at Russia's deadliest onslaught on Kyiv since July - which also damaged the EU's delegation in the Ukrainian capital.

Fifteen people including four children were killed and dozens more wounded in the bombardment, Ukrainian officials said.

A five-storey residential building was destroyed, and the EU office and nearby British Council were damaged.

In a strongly worded statement, von der Leyen said that Russian missiles struck in close proximity to the diplomatic mission: "Two missiles hit in a distance of 50m (165ft) of the delegation within 20 seconds."

The overnight attacks followed a US-led diplomatic offensive aimed at bringing an end to the war and infuriated the UK as well as the EU.

UK Prime Minister Sir Keir Starmer accused Russia's Vladimir Putin of "sabotaging hopes of peace", while EU foreign policy chief Kaja Kallas said they showed "a deliberate choice to escalate and mock peace efforts".

Moscow had chosen "ballistics instead of the negotiating table", said Ukrainian President Volodymyr Zelensky, who reiterated the need for "new, tough sanctions" on Russia.

Although the Kremlin said Russia was "still interested" in negotiations, von der Leyen said the strikes were "another grim reminder" that Russia would "stop at nothing to terrorise Ukraine", killing men, women and children and even targeting the EU.

An EU spokeswoman said no diplomatic mission should ever be targeted and the Russian charge d'affaires in Brussels was being summoned in response to the attack. The UK said Russia's ambassador to London, Andrey Kelin, would be summoned to the foreign office.

Ukrainian forces said Russia had fired almost 600 drones and more than 30 ballistic and cruise missiles - the biggest attack on the capital this month.

Many of those killed in Kyiv were in the five-storey residential building in the south-eastern Darnytskyi district on Kyiv's left bank.

The missile that hit at around 03:00 on Thursday went straight through the block of flats, causing it to collapse.

During the morning diggers removed rubble and rescue workers clambered on top of parts of the building that were still burning looking for survivors.

Ten people lived in that section of the building alone and authorities said they had not yet been able to reach them.

Officials said three of the children killed were aged two, 14 and 17.Several other youngsters were wounded.

The wave of missiles came after more than 100,000 Ukrainian homes were left without power by Russian drone attacks on energy infrastructure on Wednesday. Another 60,000 consumers were left without power in the central Vinnytsia region in the latest attacks, officials said.

Zelensky said the attack on Ukraine's cities and communities was a clear response from the Kremlin to everyone who had called for weeks and months "for a ceasefire and for real diplomacy".

European Council President António Costa said he was "horrified" by the latest Russian attacks. The British Council, which fosters cultural relations with other countries and is housed in the same block as the EU's mission, said its office was severely damaged and would be closed to visitors until further notice.

Ursula von der Leyen said the EU was preparing a 19th package of sanctions on Russia and announced she would visit seven EU member states who shared a border with Russia and its ally Belarus over the next few days.

The Commission said she would go to Latvia and Finland on Friday before going on to Estonia, Poland, Bulgaria, Lithuania and Romania.

Dmitry Vlasov

BBC correspondent Dmitry Vlasov photographed parts of Kyiv affected by the shellingRescue crews outside an apartment building that was destroyed in the strike

US President Donald Trump had hoped to organise a summit involving Zelensky and Russia's Vladimir Putin to bring an end to the war, but those efforts have so far failed.

He first met Putin in Alaska before holding talks with Zelensky and European leaders in Washington.

Ukraine's president has backed the move, but the Kremlin has played down any chance of a Putin-Zelensky summit.

Despite the latest setback, US officials will hold talks with a Ukrainian delegation in New York on Friday. Zelensky said they would discuss "military, political and economic components of security guarantees" for Ukraine.

Ukraine is working with its European allies on guarantees aimed at preventing any future Russian attack in the event of a peace deal. Zelensky had talks in Kyiv this week with the head of Britain's armed forces, Adm Sir Tony Radakin.

Russia says it will not accept European troops on the ground and says discussing them without Moscow's involvement is a "road to nowhere".