The hostilities, which entered their fourth month Tuesday, have killed thousands of people, displaced more than eight million and forced more than six million refugees to flee across the borders.

"We will continue the special military operation until all the objectives have been achieved, regardless of the massive Western aid to the Kyiv regime and the sanctions against Russia," Defence Minister Sergei Shoigu told regional counterparts from the Russia-led Collective Security Treaty Organization.

He added that Moscow's efforts to avoid civilian casualties "are of course slowing down the pace of the offensive, but this is deliberate".

Separately, the secretary of Russia's Security Council, Nikolai Patrushev, said that Moscow's offensive would last as long as necessary.

"We are not rushing to meet deadlines," Patrushev told the Russian newspaper Argumenty i Fakty in an interview published on Tuesday.

"All the goals set by the President of Russia will be fulfilled," Patrushev added.

"It cannot be otherwise, because the truth, including historical truth, is on our side."

Putin sent troops to Ukraine to "de-militarise" and "de-nazify" pro-Western Ukraine.

Russia is believed to have suffered significant human and material losses in Ukraine even though precise details have not been revealed by the Kremlin.

Western support has helped Ukraine hold off its neighbour's advances in many areas, including the capital Kyiv. Russia is now focused on securing and expanding its gains in Donbas and the southern coast.