Antonio Guterres raises alarm over ‘dangerous escalation’ after hours-long Russian drone and missile barrage this week.

United Nations Secretary-General Antonio Guterres has condemned a Russian drone and missile attack against Ukraine this week that has been described as the largest such assault in the three-year war.

In a statement on Saturday, Guterres’s spokesperson said the Russian strikes “disrupted the power supply to the Zaporizhzhia Nuclear Power Plant, once again underlining the ongoing risks to nuclear safety”.

“The secretary-general is alarmed by this dangerous escalation and the growing number of civilian casualties,” the statement read.

Ukrainian officials said Moscow fired more than 500 drones and 11 missiles at the capital Kyiv overnight into Friday in an attack that killed one person, injured at least 23 others and damaged buildings across the city.

The sounds of air raid sirens, kamikaze drones and booming detonations reverberated until dawn.

Ukraine’s President Volodymyr Zelenskyy called the attack “deliberately massive and cynical”.

Russia has been stepping up its long-range attacks on Ukrainian cities as United States-led efforts to reach a ceasefire to end the war have stalled.

On Saturday, Ukraine’s top military commander, Oleksandr Syrskii, warned of a possible new Russian offensive in the Kharkiv region, a part of northeastern Ukraine that has seen heavy fighting since Russia invaded in 2022.

Moscow has been slowly grinding its way along several parts of the Ukrainian front line in recent months, throwing forth continuous waves of infantry as it seeks to press home its advantage in troops and munitions.

Russian forces have already pushed into northern Ukraine’s Sumy region over the past months, carving out a small foothold there.

Russia fired 322 drones and decoys into Ukraine overnight into Saturday, Ukraine’s air force said. Of these, 157 were shot down and 135 were lost, likely having been electronically jammed.

Ukraine has also ramped up its retaliatory strikes in Russia, with the Ministry of Defence saying it shot down 94 Ukrainian drones overnight into Saturday, along with 45 further drones in the morning and early afternoon.

Four Ukrainian drones also were shot down while approaching Moscow on Saturday, according to Mayor Sergei Sobyanin. Meanwhile, a woman was killed in a Ukrainian drone attack in the Rostov region, the acting governor said.

Separately, the Ukrainian military said in a statement on social media on Saturday that its special forces struck Russia’s Borisoglebsk military airfield in the Voronezh region, hitting a glide bomb store and a trainer aircraft.

The military said that other aircraft were also likely hit, without giving details.

The governor of Voronezh, Alexander Gusev, wrote on Telegram that more than 25 drones were destroyed over the region overnight. He said a power line was temporarily damaged, but made no mention of a military airfield.

The attacks come as Ukraine’s Zelenskyy said on Friday that he had a “very important and fruitful” phone conversation with US President Donald Trump in his efforts to strengthen Ukraine’s air defences.

The US president also spoke to his Russian counterpart, Vladimir Putin, a day earlier in a conversation that he said was disappointing.

“I’m very disappointed with the conversation I had today with President Putin, because I don’t think he’s there, and I’m very disappointed,” Trump said after the call on Thursday. “I’m just saying I don’t think he’s looking to stop, and that’s too bad.”

Kremlin spokesperson Dmitry Peskov said on Friday that it was “preferable” to achieve the goals of Russia’s invasion through political and diplomatic means.

“But as long as that is not possible, we are continuing the special operation,” he said.