American Marconi Wireless News - Ukraine, Russia vow escalation after Moscow strikes on Kyiv kill 25

Ukrainian President Volodymyr Zelensky said his forces would "definitely" retaliate for the overnight pummelling as he inspected an apartment block that was partially destroyed.

The European Union's top diplomat proposed new sanctions on Moscow, as Zelensky pressed the United States for licences to manufacture Patriot air-defence missiles.

UN chief Secretary-General Antonio Guterres condemned Russia's barrage and repeated a ceasefire call.

"Attacks against civilians and civilian infrastructure wherever they occur are a clear violation of international humanitarian law and must stop immediately," said his spokesman Stephane Dujarric.

But the Kremlin vowed to further ramp up "pressure" on Kyiv, sticking to its no-compromise rhetoric.

- 'Most massive attack' -

Russia has routinely launched waves of missiles and drones during its invasion, Europe's deadliest conflict since World War II.

AFP journalists in central and eastern Kyiv heard more than a dozen explosions and saw residents rushing to shelter in metro stations.

In the morning, locals stood on the rubble of destroyed apartment blocks ripped apart by the barrage, as smoke poured over the Kyiv skyline.

Blasts started echoing out late on Wednesday, lasting into the early hours of Thursday as Russian missiles and drones rained down on residential areas in the city centre.

Mayor Vitali Klitschko described it as the "enemy's most massive attack on the capital".

The state emergency services said at least 25 people had been killed and others were missing.

The Ukrainian branch of the Red Cross said its key warehouse had been destroyed and around $2 million worth of humanitarian aid lost.

Debris also damaged a building "hosting a number of diplomats", EU spokeswoman Anitta Hipper told AFP, adding that the EU diplomats were safe.

Kyiv urged its allies to send more air defence.

"We also very much count on a decision by the United States regarding licences for Patriots," Zelensky said in a post on Facebook.

Later, after talks with Finland's President Alexander Stubb, he added: "Defending against ballistic missiles is impossible without a sufficient number of missiles for Patriot systems."

Ukraine wants to manufacture munitions for the US-made missile interceptor system, but defence experts say it would take time to set up production domestically.

A US official told AFP President Donald Trump wanted a peace deal to end the "senseless killing" in Ukraine.

- Struggling to sleep -

Russia fired 496 drones and 74 missiles, including hard-to-intercept ballistic projectiles, Ukraine's air force said.

It said it shot down 48 of the missiles and 476 drones.

AFP reporters met several Kyiv residents outside an apartment building largely destroyed in the attack.

"Half the building has been destroyed. The roof is gone," said 32-year-old factory worker Sabina Mambetova, standing outside the rubble of her home in the eastern Darnytskyi district.

"I've been left without an apartment, alone with my child. I don't know what to do now."

Some 52,000 people, including 4,500 children packed into underground stations to shelter from the barrage -- the highest number in recent years, according to the Kyiv metro.

Others hunkered down in basements or corridors through the night as blasts shook buildings across the city.

"It's hard," 32-year-old doctor Kateryna Kucheryava told AFP from the metro as the attack was unfolding. "My child is used to sleeping in complete silence and darkness.

"I picked her up and carried her down. She woke up and now she's not sleeping anymore."

Along station platforms, locals set up tents and lay on air mattresses and camping chairs, while mothers tried to sleep clutching babies to their chests.

- Zelensky cuts short visit -

The EU's top diplomat Kaja Kallas said she would propose new sanctions on Moscow over the attack.

The attack came hours after Zelensky cut short a visit to Dublin on Wednesday, citing intelligence reports of an impending Russian strike.

Zelensky said Russian President Vladimir Putin "has been preparing this massive strike against Ukraine for some time now".

Ukraine has stepped up long-range drone attacks inside Russia in recent weeks, targeting energy infrastructure and military targets.

L.Miller--AMWN