A wave of strong explosions rang out in Kyiv, AFP journalists said early Tuesday, as Russia resumed strikes on the Ukrainian capital after a three-day halt.
Russian President Vladimir Putin had ordered the pause in attacks as US President Donald Trump's envoys Steve Witkoff and Jared Kushner visited the Russian and Ukrainian capitals at the weekend.
The fresh explosions triggered fires and car alarms in the city, and Kyiv's mayor Vitali Klitschko said that six people were wounded.
The Ukrainian army's air force reported a missile attack, with the Kyiv city military administration urging residents to take shelter as the air defence system was in operation.
The strikes damaged buildings across the capital, including a five-storey apartment block in the Solomianskyi district, while vehicles caught fire in the Podilskyi district, authorities said.
Klitschko said people were trapped in a residential building.
The attack is the first targeting Kyiv after the expiration of a three-day halt for the US envoys' visit to the Russian and Ukrainian capitals.
Russia's state news agency TASS confirmed earlier that the pause in strikes had expired.
Air alerts were active in a dozen regions across Ukraine by 5:30 am (0230 GMT).
Telegram channels monitoring air threats on Ukraine said Russia had started to transport ballistic missiles and relocate heavy bombers from the country's east to airfields closer to Ukraine.
Poland also announced "aviation operations" had commenced following the Russian attack.
- US proposals -
Witkoff touted on Monday "substantive progress" had been made in the discussions with Ukraine and Russia, raising the prospect of reviving three-way peace talks to end Europe's deadliest conflict since World War II.
"President Trump is working hard to stop the killing and work towards a lasting and durable peace," he said on X.
Witkoff and Kushner met Putin in Moscow on Saturday, before holding separate talks with Ukrainian President Volodymyr Zelensky in Kyiv in their first official trip to the city.
The Kremlin announced Monday that it did not rule out three-way talks, with spokesman Dmitry Peskov telling reporters "it is too early to say anything about the venue or the exact dates at this stage".
Zelensky said he and his negotiating team were "coordinating our next steps" following the talks with Trump's envoys and European officials, but the Ukrainian leader did not elaborate on what those steps would be.
A senior Ukrainian official told AFP on Sunday that the two envoys had brought new and "more effective" proposals on ending the war without giving further details, but Zelensky warned that fighting appeared likely to continue into the winter.
During previous negotiations, Moscow and Kyiv had broadly stuck to their positions, with talks stalling in particular over the issue of territories in eastern Ukraine of which Russia claims.
Zelensky says Russia 'ready to negotiate'
Ukraine's President Volodymyr Zelensky said Monday that Russia showed readiness to negotiate towards a conflict settlement at talks with US envoys, Axios reported.
The weekend visit to Moscow and Kyiv by Steve Witkoff and Jared Kushner marks Washington's latest bid to break a diplomatic stalemate in Europe's deadliest conflict since World War II, which began with Russia's full-scale invasion of Ukraine four years ago.
Witkoff touted progress in the meetings and raised the prospect of reviving three-way peace talks to end the war.
Zelensky told US news outlet Axios that the United States was pushing to de-escalate the conflict ahead of the long winter.
Russia has struck Ukraine's energy grid each winter since invading in February 2022, cutting power and heating to millions in temperatures as low as -20C.
Zelensky said the US envoys -- who held separate talks with the Ukrainian and Russian leaders -- told him that "the Russians are ready to negotiate".
"Russia really thinks that this winter can help them to break us," he told Axios.
But the administration of US President Donald Trump could pressure Russian President Vladimir Putin to de-escalate, he added, and Putin "doesn't want" to "upset" his US counterpart.
Zelensky said the weekend talks included US proposals around energy facilities, grain shipments and oil and gas exports, but declined to give further details.
The Ukrainian leader said the US approach aimed to resume negotiations between the warring countries and ensure the coming winter was different from previous ones.
The goal was to make progress before or during winter in order to "bring (the) sides closer to the peace," Zelensky said.