With Moscow's "special military operation" now approaching another winter, both sides have been digging deep and procuring weapons from allies in preparation for a protracted conflict.

The announcement came as NATO chief Jens Stoltenberg and the defence ministers of Britain and France visited Kyiv, where President Volodymyr Zelensky lobbied for more air defence systems.

"We need to get through this winter together, to protect our energy infrastructure and people's lives," Zelensky told Stoltenberg, warning of a fresh campaign of Russian attacks after last year's strikes left millions short of water and heating.

Ukraine's newly appointed defence minister Rustem Umerov, after meeting with his British counterpart Grant Shapps, said "winter is coming but we are ready".

Shapps said he was in Kyiv for his first visit to discuss with Zelensky "what he needs to win".

Ukraine has repeatedly asked for more Western weapons, including longer-range missiles, to help break through Russian positions and launch strikes deep within Russian-controlled territory.

Kyiv began its counter-offensive in June but has acknowledged slow progress.

- 'Imperialist delusions' -

Stoltenberg accepted that Ukraine's army was facing "fierce fighting" as it slowly claws back territory from Russian forces, but said Kyiv was gaining ground.

"Every metre that Ukrainian forces regain is a metre that Russia loses. Moscow is fighting for imperialist delusions," he said.

The speed of Ukraine's advances has raised concerns in some Western countries over Kyiv's military strategy, but Stoltenberg again vowed that the US-led defence bloc was unwavering in its support.

"NATO will stand with Ukraine for as long as it takes," he told Zelensky, adding that Ukraine is "closer to NATO than ever before."

Zelensky said it was a "matter of time" before Ukraine joins the alliance.

When the Kremlin launched its large-scale military operation in Ukraine last year it had hoped to topple the Ukrainian government within days.

But the conflict has dragged on and Russia has ramped up arms manufacturing and pumped massive funds into its military machine, despite persistently high inflation and a weaker ruble.

According to a finance ministry document published Thursday, defence spending is set to jump by over 68 percent year-on-year to almost 10.8 trillion rubles ($111.15 billion) -- more than spending allocated for social policy.

- 'Hybrid war' -

"It is obvious that such an increase is necessary, absolutely necessary, because we are in a state of hybrid war, we are continuing the special military operation," Kremlin spokesman Dmitry Peskov said.

"I'm referring to the hybrid war that has been unleashed against us," he said.

Russian authorities have repeatedly accused Western powers of de facto fighting against Moscow through their military and other support to Ukraine.

Defence spending in 2024 is set to total around three times more than education, environmental protection and healthcare spending combined, figures calculated by AFP showed.

"The focus of economic policy is shifting from an anti-crisis agenda to the promotion of national development goals," the finance ministry said in the document.

It said this included "strengthening the country's defence capacity" and "integrating" four Ukrainian regions Moscow claims to have annexed last year.

President Vladimir Putin and other officials have largely shrugged off the economic effects of the Ukraine offensive.

But Russia's central bank warned this month that economic growth was set to slow in the second half of 2023.

Russia has sought to portray that it has reliable allies against the West.

But on a visit to Berlin Thursday, the leader of Russia's ally Kazakhstan vowed that his country will "follow the sanctions regime" against Moscow.

"There should not be any concerns on the German side about possible actions aimed at circumventing the sanctions regime," Kazakh President Kassym-Jomart Tokayev said.

Kazakhstan has not recognised eastern and southern Ukrainian regions occupied by Moscow as part of Russia and has been rattled by the full-scale offensive.

- Drones and cruise missiles -

The visits came ahead of Kyiv's first Defence Industries Forum, where Ukrainian officials were to meet representatives from over 160 defence firms and 26 countries.

Both Moscow and Kyiv have launched systematic aerial attacks on strategic facilities with drones and cruise missiles.

Ukraine said earlier Thursday that Russia had deployed a "massive" drone attack overnight, adding that it had destroyed 31 of the 39 aircraft.

Russian unmanned aerial vehicles were intercepted over Black Sea coastal regions and further inland, it said.