Zelensky has previously warned that Russia is likely to increase air strikes against Ukraine's energy infrastructure ahead of the winter, as it did this time last year.

"My estimation is that they are accumulating [missiles], but that they don't have many more missiles compared to what they previously had," Zelensky said, referring to attacks last year on critical infrastructure.

Kyiv in response has urged its allies abroad to bolster its air defence systems to stave off a repeat of last year's strikes, which left millions of people in the cold and dark for extended periods.

"In terms of air defence, we are better than we were last winter," Zelensky said during a meeting with reporters in the capital.

He added that authorities had built more bomb shelters and increased aid points where civilians could keep warm and charge phones in the event of power outages caused by air strikes.

But Zelensky warned in separate comments that Ukraine did not have "100 percent protection" from Russian aerial attacks.

"Cities like Kharkiv, regions like Donetsk and Zaporizhzhia, need more [air defence] systems," he said in an evening address posted on social media.

He also told reporters that Western sanctions imposed on Russia in response to the war had slowed Russia's production of missiles, but that Moscow's supply of attack drones was "more or less fine".

"Winter will be difficult but not worse than the previous one," Zelensky said.