A barrage of Russian missiles targeted Kyiv, wounding at least 53 people, officials said, as Ukrainian President Volodymyr Zelenskyy sought more military support in Europe after a trip to Washington secured no new pledges.

Loud explosions rocked Ukraine’s capital at 3am as the city’s air defences were activated for the second time this week. Ukraine’s air force said Russia launched 10 ballistic missiles toward Kyiv and all were intercepted by air defences, but their debris struck homes and a children’s hospital.

The attack underscored the continuing threat to Ukraine from the Kremlin’s missile arsenal in the 21-month war. Russia has been stockpiling its air-launched cruise missiles from its heavy bomber fleet, according to a recent assessment by the UK Ministry of Defence.

That may herald another heavy winter bombardment of Ukraine’s power grid. Moscow last year targeted energy infrastructure in an effort to deny Ukrainians heat, light and running water and break their fighting spirit.

As winter sets in and hinders troop movements, allowing little change along the front line, long-range air bombardment plays a growing role.

Ukraine has dwindling supplies of air defence munitions and other ammunition. That prompted Zelenskyy to visit Washington in an effort to persuade lawmakers to approve US President Joe Biden’s request for $61.4 billion ($98.7b) for Ukraine. His trip accomplished no breakthrough.

People stand near a crater in the yard of a damaged multi-store building after a Russian attack on a residential neighbourhood in Kyiv, Ukraine. Photo / AP

Zelenskyy said on Telegram he and Biden agreed to work on increasing the number of air defence systems in Ukraine. “The terrorist state has just demonstrated how crucial this decision is,” Zelenskyy said, referring to the overnight strikes.

On Wednesday, he met in Oslo with Nordic leaders who feel the potential threat from nearby Russia keenly and are among Kyiv’s staunchest supporters.

Zelenskyy may also attend a European Union summit in Brussels, where the continent’s leaders are expected to discuss their backing for Ukraine. Officials did not confirm such a trip.

• 'Brutality, criminality, and depravity': US files war crime charges against Russian soldiers
• Ukraine insists it sees no sign of Nato war fatigue

“Russia is eager to exploit divisions,” the senior leaders from Denmark, Iceland, Norway, Finland and Sweden said in a joint statement in Oslo. “We must continue to stand united against Russia’s illegal and immoral war.”

They vowed “comprehensive assistance” for Ukraine. “Now is not the time to tire,” the Nordic leaders said, amid signs of war fatigue among Kyiv’s foreign supporters.

Danish Prime Minister Mette Frederiksen said her government will unveil a Ukraine support package of almost €1 billion ($1.7 billion) this week. Norway announced it will give additional air defences to Ukraine, taking them from its own stocks to ensure speedy delivery.

Separately, Latvia and Ukraine announced an agreement on the production of drones, a key part of the war.

In the overnight missile attack, debris from the intercepted weapons fell in Kyiv’s eastern Dniprovskyi district, injuring dozens of people, Kyiv Mayor Vitali Kitschko said on Telegram. Twenty people, including two children, were hospitalised, and 33 people received medical treatment on the spot.

An apartment building, a private house and several cars caught fire, while the windows of a children’s hospital were shattered, Klitschko said. Falling rocket debris also damaged the water supply system in the district.

Elsewhere in Ukraine, 10 Russian drones were shot down, most of them in the Odesa region, the Ukrainian air force said.

In other developments, a “hacktivist” group called SoIntsepek claimed responsibility for a major cyber-attack on Tuesday against Ukrainian internet and cellphone provider Kyivstar, which serves more than 24 million mobile customers across the country.

The Google-owned US cybersecurity firm Mandiant said SoIntsepek regularly claims credit for the activity of the Russian hacking team known as Sandworm, part of the GRU military intelligence agency.

“The persona was probably fabricated by the GRU to launder their operations publicly,” Mandiant threat analyst John Hultquist said in an emailed statement, adding that Sandworm is responsible for “most major disruptive cyber-attacks we know about”.

A Kyivstar spokeswoman said the company hoped to restore all service, but the network integrity company Kentik Inc. said only a fraction had been restored by the afternoon.

Meanwhile, the Organisation for Security and Co-operation in Europe said in a report Russian forces this year have “continued to use explosive weapons with wide area effects in their attacks on densely populated urban areas of Ukraine ... both in areas close to heavy fighting and in cities far from the contact line”.

The governmental organisation added to the report that Ukrainian armed forces, though on a much smaller scale, also shelled populated areas of Ukraine that are occupied by Russia, causing civilian casualties and damage to civilian infrastructure.