Ukrainian President Volodymyr Zelenskyy reiterated denial of his country's responsibility for an alleged drone attack on the Kremlin, which Moscow says targeted President Vladimir Putin.
Russian officials said Putin was not in the Kremlin at the time of the attack.
"We don't attack Putin, or Moscow, we fight on our territory," Zelenskyy told a news conference in Helsinki, where he is attending a meeting with Nordic leaders.
The Ukrainian president suggested that Russia staged the attack because "Putin needs to motivate his people" after a shortage of Russian victories in the ongoing war.
He said Kyiv will leave it to a war tribunal to determine responsibility for the alleged attack.
Ukraine presidential adviser Mykhailo Podolyak had earlier sent out a note to various media outlets, saying Kyiv had "nothing to do with the drone attacks on the Kremlin."
"We do not attack the Kremlin because, first of all, it does not resolve any military tasks," the Reuters news agency quoted him as saying.
Podolyak warned that Russia would use the attack "to justify massive strikes on Ukrainian cities, on the civilian population, on infrastructure facilities" in coming days, the Associated Press quoted him as saying.
He added to Reuters that the attack "clearly indicates the preparation of a large scale terrorist provocation by Russia in the coming days."
Russia claimed it thwarted a drone attack on the Kremlin overnight, which it claims was a Ukrainian attempt to target Putin.
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#BREAKING: Russia says Ukraine tried to attack the Kremlin with drones in a move to target President Vladimir Putin, alleges terrorist act underscoring its right to respond. pic.twitter.com/lEgwxVUieT
Russian emergency responders have extinguished a fire at an oil refinery on Thursday.
The fire reportedly broke out in the Black Sea port of Novorossiysk after a drone attack, setting alight tanks that contained oil products.
The incident comes not long after Russia reported a drone attack on the Kremlin, and days after an attack on a Russian oil depot in Crimea. Ukraine rarely claims responsibility for attacks in Russia or Crimea.
Explosions heard in Kyiv
Loud explosions could be heard in Kyiv in the early hours of Thursday morning.
"Air defenses are working in the Kyiv region," the regional military administration said on Telegram.
Local media also reported explosions in Zaporizhzhia and Odesa.
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