President Volodymyr Zelenskiy said on Thursday that large-scale Russian attacks overnight in various parts of Ukraine showed Moscow was avoiding negotiations about ending the more than three-year-old war.

Vladimir Putin is demanding that Ukraine give up all of the eastern Donbas region, renounce ambitions to join NATO, remain neutral and keep Western troops out of the country, three sources familiar with top-level Kremlin thinking told Reuters.

Russia struck an American business with cruise missiles overnight in one of the largest aerial attacks of the war so far, Ukraine has said.

Russia launched a massive overnight assault on Ukraine, firing 614 projectiles in what marks the most extensive aerial strike in three weeks. The Ukrainian Air Force reported intercepting or electronically jamming 546 drones and decoys, along with 31 missiles. Despite these efforts, strikes landed in 11 locations, including in Western Ukraine.

Russian troops currently control about 20% of Ukrainian territory, but the Ukrainian constitution forbids giving up territory or trading land.

Russia said Wednesday attempts to resolve security issues relating to Ukraine without Moscow's participation were a "road to nowhere," and that much diplomatic work needs to be done before Vladimir Putin and Volodymyr Zelenskyy are ever in the same room.

The second Oval Office meeting in six months between U.S. President Donald Trump and Ukrainian President Volodymyr Zelenskyy went off smoothly, in sharp contrast to their disastrous encounter in February.

Last month was the deadliest since Putin launched his full-scale war on Ukraine three and a half years ago. In July alone, 286 civilians were killed and another 1,388, according to official data.

Moscow is preparing to raise taxes and cut spending as it tries to maintain high defence expenditure with Russia's economy creaking under the weight of financing the more than three-year war in Ukraine,

At a ceremony in Pyongyang, Kim Jong Un praised the overseas troops and said their participation demonstrated "the power of the heroic (North Korean) army."