Russia launched one of its largest air strikes on Kyiv in over three years of war and struck a maternity ward in the southern city of Odesa in attacks that killed at least two people, officials said on Tuesday.

The overnight strikes followed Russia’s biggest drone assault of the war on Ukraine on Monday and were part of intensified bombardments what Moscow says is retaliation for attacks by Ukrainian forces on Russia.

Loud explosions shook Kyiv and blasts and fires lit up the sky in the early hours of Tuesday morning, leaving palls of heavy smoke over the city, Reuters witnesses said.

At least four people were treated in hospital after seven of the capital's 10 districts were hit, city officials said.

“Today was one of the largest attacks on Kyiv,” President Volodymyr Zelenskiy said. “Russian missile and Shahed (drone) strikes drown out the efforts of the United States and others around the world to force Russia into peace.”

Zelenskiy urged Ukraine's allies to take steps to force Russia into peace, and Ukrainian Foreign Minister Andrii Sybiha called for immediate new sanctions and air defence systems.

Although Moscow and Kyiv have held two rounds of direct peace talks in recent weeks, the only tangible progress has been an agreement on exchanges of prisoners of war, and Russia has continued to advance along the front line in eastern Ukraine.

Moscow and Kyiv blame each other for the lack of progress towards ending the war, which has raged since Russia's full-scale invasion in February 2022, and US President Donald Trump has expressed frustration with both sides.

Russia temporarily halted flights overnight at four airports serving Moscow, at St Petersburg’s Pulkovo Airport and at airports in nine other cities after the Defence Ministry said Ukraine had launched more drones at Russia, officials said.

Flights in Moscow and some other cities were later restored but restrictions were still in place in St Petersburg at 0430 GMT. No damage was reported.

‘DIFFICULT NIGHT’

Ukraine’s air force said Russia had fired 315 drones across the country, of which 277 were downed. All seven missiles launched by Russia were also brought down, it said.

Air raid alerts in Kyiv and most Ukrainian regions lasted five hours until around 5 am (0200 GMT), according to information released by the military.

“A difficult night for all of us,” Timur Tkachenko, head of Kyiv’s city military administration, said on Telegram.

Moscow has intensified attacks on Ukraine following Kyiv’s strikes on strategic bombers at air bases inside Russia on June 1. Moscow also blamed Kyiv for bridge explosions on the same day that killed seven and injured scores.

Over the past week, Russia has launched 1,451 drones and 78 missiles to attack the country, according to Ukrainian air force data.

In the southern port of Odesa, an overnight drone attack hit an emergency medical building, a maternity ward and residential buildings, regional governor Oleh Kiper said on Telegram.

Two men were killed in the attack on the city but patients and staff were safely evacuated from the maternity hospital, he said.

Both sides deny targeting civilians but thousands of civilians have been killed in Europe’s worst conflict since World War Two, the vast majority of them Ukrainian.