A Russian strike on Ukraine's western city of Ternopil killed at least 20 people, including two children, casting doubt on President Volodymyr Zelensky's attempts to "reinvigorate" the peace process with talks in Turkey later Wednesday.

The early morning strike was the deadliest attack on Ukraine for weeks and one of the worst on the west of the country, hundreds of miles from the front, since Moscow invaded in 2022.

Rescuers pulled bodies from the wreckage throughout the morning after an attack that added to questions about what Zelensky could achieve in Turkey -- as doubts also grew over whether US envoy Steve Witkoff would join the talks.

Images released by officials showed several floors of a high-rise residential building blown apart, with rescue workers going through blown-out windows.

"The number of casualties from the Russian missile strike on Ternopil has risen to 20 people, including two children," Ukraine's state emergency service said on social media.

The interior ministry said another 66 people were wounded, including 16 children.

City streets were covered with debris and parts of the city engulfed in thick grey smoke after explosions were reported around 7:00 am (0500 GMT).

"This is how Russia's 'peace plans' look like in reality," Ukrainian Foreign Minister Andriy Sybiga said.

In Moscow, the Kremlin declined to comment on a report by US media outlet Axios that it had been working on a secret peace plan with the United States to end the almost four-year-long war.

The strike comes as Russia batters Ukraine's energy grid ahead of the winter, and with Ukraine's stretched troops under pressure on the front line.
 
- 'Insufficient' pressure -
 
Ternopil officials also reported the large fires had caused chlorine levels in the air to spike to six times the norm, and called on the city's 200,000 residents to stay home and close their windows.

Kyiv's air force said Russia had fired more than 476 drones and 48 missiles overnight.

The overnight attacks also wounded at least 46 people in the northeastern region of Kharkiv, and targeted other areas of western Ukraine.

Neighbouring Romania scrambled fighter jets as it reported a Russian drone had crossed into its airspace, while Moldova also said its airspace was breached at night.

Ahead of his talks in Turkey, Zelensky called on Ukraine's Western backers to do more to get Russia to end the war.

"Every brazen attack against ordinary life shows that the pressure on Russia is insufficient," he said.

A day earlier he said the trip to Ankara would "reinvigorate" frozen peace talks.

A senior Ukrainian official told AFP the "main goal is for the Americans to re-engage" in peace efforts.

Kyiv hopes Washington will be able to push Russia to the negotiating table, including by imposing sanctions, the official said.

But media reports claimed US envoy Witkoff had cancelled a planned trip to join.

The head of Zelensky's office, Andriy Yermak, said he was in "constant communication with representatives of President (Trump)'s administration, including US Special Envoy Steve Witkoff," but did not say if he would meet him in Turkey.

Witkoff has not said if he will travel.
 
- US-Russia plan -
 
Zelensky will meet Turkish counterpart Recep Tayyip Erdogan in Ankara in the afternoon, where he said they would "discuss the best ways to ensure Ukraine achieves a just peace".

Turkey has hosted three rounds of Russia-Ukraine talks this year that have yielded only prisoner exchanges and the repatriation of killed soldiers' bodies.

The Kremlin said no Russian official would be at the talks, but that it remained open to negotiations to resolve the conflict.
Returning to the White House in January, Trump had sought to leverage his personal chemistry with Russian leader Vladimir Putin to end the war, but has so far failed to make progress.

Russian troops are making slow but steady advances on the front and Putin has demanded Kyiv cede more territory and renounce Western military support if it wants Moscow to halt its invasion.