Russian missile attacks have hit critical infrastructure in Kyiv and the eastern city of Kharkiv, officials say, as the governor of another region warns a massive missile strike could follow in the coming hours.
Reuters journalists heard a series of blasts in Kyiv before the air raid siren even sounded, which is highly unusual.
Officials told residents to stay in shelters.
"Explosions in Dniprovskiy district. All agencies heading to the site. Stay in your shelters!" Kyiv Mayor Vitali Klitschko wrote on the Telegram messaging app.
Russia, which invaded last February, has been pounding Ukraine's vital energy infrastructure with missiles and drones since October, causing sweeping blackouts and disruptions to central heating and running water as winter bites.
"Missile attack on critical infrastructure facilities. Details are being checked," said Kyrylo Tymoshenko, deputy head of the president's office.
Oleg Synehubov, Kharkiv's regional governor, said two S-300 missiles struck the city near the Russian border early on Saturday.
The attacks hit critical energy infrastructure and industrial facilities in the Kharkiv and Chuhuev districts of the region, he said.
"Our emergency services units and energy workers are working to liquidate the consequences and stabilise the situation with energy supplies," he said.
In Kyiv, the mayor said the debris of a missile came down on a non-residential area in the Holosiivskiy district in the west of Kyiv, causing a fire but hurting no one.
Residential infrastructure was also hit in the village of Kopyliv in the Kyiv region just outside the capital.
The windows and roofs of 18 privately owned houses were shattered or damaged by the blast, Oleksiy Kuleba, the regional governor, said.
The governor of the central Cherkasy region warned a massive Russian missile strike could follow later on Saturday, while the governor of Mykolaiv to the south said 17 Russian Tupolev warplanes had taken off from their air bases.
But after their statements, the air raid alarm in Kyiv and the surrounding region was lifted.
The strikes on Saturday came as Ukrainian and Russian forces battled for control of Soledar, a small salt-mining town in eastern Ukraine that has for days been the focus of a relentless Russian assault.
Russia said on Friday its forces had taken control of Soledar, in what would be a rare success for Moscow after months of battlefield reverses but Kyiv said its troops were still fighting in the town.
Reuters could not immediately verify the situation in Soledar.
Kyiv and the West have played down the town's significance, saying Moscow sacrificed wave upon wave of soldiers and mercenaries in a pointless fight for a bombed-out wasteland, unlikely to affect the wider war except insofar as the huge losses have sapped manpower on both sides.
But the capture of the town has taken on an outsized importance as it would, if confirmed, give Moscow a trophy for one of the bloodiest campaigns of the war following major battlefield setbacks throughout the second half of 2022.
"The capture of Soledar was made possible by the constant bombardment of the enemy by assault and army aviation, missile forces and artillery of a grouping of Russian forces," Moscow's defence ministry said on Friday.
Seizing the town would make it possible to cut off Ukrainian supply routes to the nearby city of Bakhmut and trap remaining Ukrainian forces there, it said.
Moscow has been trying to seize Bakhmut for months.
"The situation in Soledar is near critical - the city is semi-encircled. Only one road is left to supply our troops," said Oleh Zhdanov, a military analyst based in Kyiv.
Zhdanov, speaking in a social media video, said Russia had brought in airborne troops as reinforcements.
Ukraine's eastern military command representative Serhiy Cherevatyi told Reuters by telephone Soledar had not been captured.
"Our units are there. The town is not under Russian control," Cherevatyi said.
In an evening video address, Ukrainian President Volodymyr Zelenskiy said fighting for Soledar continued.
"The difficult battle for the Donetsk region continues. The battle for Bakhmut and Soledar, for Kreminna, for other cities and villages in the east of our country continues," Zelenskiy said.