Russian forces are continuing their attacks against the Ukrainian capital of Kyiv after what US analysts described as the largest drone strike since Moscow's invasion began.

Ukraine's Commander-in-Chief Valerii Zaluzhnyi said on Monday that Russia carried out an attack involving 40 cruise missiles and 35 drones earlier in the day. He said Ukrainians shot down 67 of the targets.

The attack came after a drone strike on Kyiv and elsewhere on Sunday, in which the Ukrainian Air Force said it shot down 52 out of 54 Iranian-made drones.

US think-tank the Institute for the Study of War said on Monday that "Russian forces conducted the largest Shahed strike against Ukraine since the start of the war."

Meanwhile, Zaluzhnyi tweeted on Saturday that "The time has come to take back what belongs to us."

Ukrainian forces are believed to have started a counteroffensive in the southern region of Zaporizhzhia, where they launched missile attacks against Russian-controlled cities.

Alina Frolova, deputy chairman of Ukraine's Centre for Defence Strategies, indicated in an interview with NHK that Ukrainians had started "shaping operations," which involve attacks on weapons storage facilities and other logistics bases.

Frolova, a former deputy defense minister, said the first option is an operation in the south to cut supplies to Crimea to isolate Russian forces.