Russian forces launched a barrage of 367 drones and missiles at Ukrainian cities overnight, including the capital Kyiv, in the largest aerial attack of the war so far, killing at least 12 people and injuring dozens more, officials said.

The dead included three children in the northern region of Zhytomyr, local officials there said.

Ukrainian President Volodymyr Zelenskiy called on the United States, which has taken a softer public line on Russia and its leader, Vladimir Putin, since President Donald Trump took office, to speak out.

"The silence of America, the silence of others in the world only encourages Putin," he wrote on Telegram.

"Every such terrorist Russian strike is reason enough for new sanctions against Russia."

It was the largest attack of the war in terms of weapons fired, although other strikes have killed more people.

Interior Minister Ihor Klymenko said 12 people had been killed and 60 more wounded. Earlier death tolls given separately by regional authorities and rescuers had put the number of dead at 13.

"This was a combined, ruthless strike aimed at civilians. The enemy once again showed that its goal is fear and death," he wrote on Telegram.

The assault comes as Ukraine and Russia prepared to conduct the third and final day of a prisoner swap in which both sides will exchange a total of 1000 people each.

CEASEFIRE EFFORTS

Ukraine and its European allies have sought to push Moscow into signing a 30-day ceasefire as a first step to negotiating an end to the three-year war.

Their efforts suffered a blow earlier this week when Trump declined to place further sanctions on Moscow for not agreeing to an immediate pause in fighting, as Kyiv had wanted.

Ukraine's air force said Russia had launched 298 drones and 69 missiles in its overnight assault, although it said it was able to down 266 drones and 45 missiles.

Damage extended to a string of regional centres, including Ukraine's second-largest city, Kharkiv, as well as Mykolaiv in the south and Ternopil in the west.

In Kyiv, Tymur Tkachenko, head of the city's military administration, said 11 people were injured in drone strikes. No deaths were reported in the capital, although four were killed in the region around the city, according to officials.

This was the second large aerial attack in two days. On Friday evening, Russia launched dozens of drones and ballistic missiles at Kyiv in waves that continued through the night.

In northeastern Ukraine, Kharkiv Mayor Ihor Terekhov said early on Sunday that drones hit three city districts and injured three people. Blasts shattered windows in high-rise apartment blocks.

Drone strikes killed a 77-year-old man and injured five people in the southern city of Mykolaiv, the regional governor said. He published a picture of a residential apartment block with a large hole from an explosion and rubble scattered over the ground.

In the western region of Khmelnytskyi, many hundreds of kilometres away from the frontlines of fighting, four people were killed and five others wounded, according to the governor.

"Without pressure, nothing will change and Russia and its allies will only build up forces for such murders in Western countries," the Ukrainian president's chief of staff Andriy Yermak wrote on Telegram.

"Moscow will fight as long as it has the ability to produce weapons."

Russia's Defence Ministry reported that its air defence units had intercepted or destroyed 95 Ukrainian drones over a four-hour period. The Mayor of Moscow, Sergei Sobyanin, said 12 Ukrainian drones had been intercepted on their way to the capital.