A massive overnight Russian attack has hit Ukraine's capital Kyiv, killing at least two people and injuring 16, President Volodymyr Zelensky has said.

The attack involved 18 missiles and about 400 drones, primarily targeting the capital, Zelensky added.

Residents' sleep was interrupted for three hours as drones and missiles converged on the capital. Authorities in Kyiv said drone wreckage struck the roof of a residential building and fires burned across the city.

In June, Ukraine recorded the highest monthly civilian casualties in three years, with 232 people killed and 1,343 injured, according to the UN.

In the early hours of Thursday morning, Ukraine's police reported that Russian drone strikes had hit eight districts in Kyiv.

"Residential buildings, vehicles, warehouses, office and non-residential buildings are burning," administration head Tymur Tkachenko said in a post on Telegram.

Interior Minister Ihor Klymenko confirmed that a 68-year-old woman and a 22-year-old police officer at a metro station had been killed.

In Kyiv's Podilsky district, a primary healthcare centre was "almost completely destroyed", Mayor Vitaliy Klitschko said.

City residents were urged to shelter until the air raid siren was lifted, and also close windows when they returned to their homes because there was a "lot of smoke" in Kyiv.

Overnight, Ukraine's air force reported a threat of Russian drone attacks in a number of regions. It was not immediately clear whether there were any casualties outside Kyiv.

Russia's military has not commented on the reported latest attack.

It followed what Ukraine described as the largest Russian aerial attack on Tuesday night, when 728 drones and 13 cruise or ballistic missiles struck cities across the country.

In June, Russia launched ten times more "missile and loitering munitions attacks" against Ukraine than in June last year, the United Nations Human Rights Monitoring Mission (HRMMU) in Ukraine reported.

Civilians were killed or injured in at least 16 regions of the country and in Kyiv, the HRMMU said.

"Civilians across Ukraine are facing levels of suffering we have not seen in over three years," Ms Danielle Bell, head of the HRMMU, said. "The surge in long-range missile and drone strikes across the country has brought even more death and destruction to civilians far away from the frontline."

Late on Wednesday, three people were killed in a Russian air strike in the town of Kostiantynivka, close to the front line in eastern Ukraine, the country's emergency service DSNS said.

"Russia is obviously stepping up terror," Zelensky said. "It is necessary to be faster with sanctions and pressure Russia so that it feels the outcomes of its own terror. Our partners need to act faster investing in weapons production and developing tech."

He said that on Thursday, he would be speaking to partners about additional financing for producing interceptor drones and air defence supplies.

The US had resumed sending some weapons to Ukraine, Reuters reported late on Wednesday, days after it halted shipments of some critical air defence arms.

The latest attack underlines just how remote the prospects of a diplomatic breakthrough seem to have become.

On Wednesday, Germany's Chancellor, Friedrich Merz, said diplomacy had been exhausted. The Kremlin spokesman, Dmitry Peskov, spoke in similar terms earlier in the week.

And US President Donald Trump seems increasingly impatient with Russian leader Vladimir Putin.

"We get a lot of bull---- thrown at us by Putin, if you want to know the truth," Trump told reporters on Tuesday. "He's very nice to us all the time, but it turns out to be meaningless."

Peskov said Moscow was "pretty calm about this. Trump's way of talking is generally quite harsh, the phrases he uses".

The two leaders have been in regular contact, but this has so far failed to translate into tangible steps towards a ceasefire in Ukraine - something Trump once said he would be able to achieve in a day.

Trump has been threatening sanctions on Russia since taking office in January but has so far not imposed any.

A bipartisan bill is working its way through Congress which would penalise countries such as China and India that continue to buy Russian oil and gas. Trump said he might support it.

The focus among Kyiv's allies has now shifted back to how to protect Ukraine and punish Russia, with Europe working on a new package of sanctions.

All this is likely to be discussed in Rome, where a two-day conference attended by delegates from 77 countries on Ukraine's recovery is due to start on Thursday.

With Russia's drone attacks on Ukraine increasing in frequency and scale, renewed attention on how to protect Ukraine's airspace could also be on the agenda.

Later on Thursday, US Secretary of State Marco Rubio is expected to meet Russian Foreign Minister Sergei Lavrov on the sidelines of a summit in Malaysia.

Putin launched a full-scale invasion of Ukraine in February 2022.