Russia invades Ukraine in a major escalation on February 24, 2022.

Nearly three months after Russia launched a bloody invasion of his country, Zelensky said there had been "few such fateful decisions for Ukraine" as the one it expects from the EU this week.

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"Only a positive decision is in the interests of the whole of Europe," he said in his evening address Sunday.

"Obviously, we expect Russia to intensify hostile activity this week ... We are preparing. We are ready," he continued.

Ukrainian President Volodymyr Zelensky speaks in Kyiv. File photo

Moscow's forces have been pummelling eastern Ukraine for weeks as they try to seize the Donbas region, after being repelled from other parts of the country following their February invasion.

On Friday, Brussels backed Kyiv's bid for EU candidate status after the heads of the bloc's biggest members -- France, Germany and Italy -- paid a visit to the Ukrainian capital.

Ukraine could join the list of countries vying for membership as early as this week, when member state leaders meet at a Brussels summit.

NATO's chief Jens Stoltenberg meanwhile warned that the war could grind on "for years" and urged Western countries to be ready to offer long-term military, political and economic aid.

Mykolaiv is a key target for Russia as it lies on the route to the strategic port of Odessa.

"We must not weaken in our support of Ukraine, even if the costs are high — not only in terms of military support but also because of rising energy and food prices," Stoltenberg told German daily newspaper Bild.

Ukraine has repeatedly urged Western countries to step up their deliveries of arms, despite warnings from nuclear-armed Russia that it could trigger wider conflict.

Zelensky made a rare trip outside Kyiv Saturday to the hold-out Black Sea city of Mykolaiv, where he visited troops nearby and in the neighbouring Odessa region for the first time since the invasion.

"We will not give away the south to anyone, we will return everything that's ours and the sea will be Ukrainian and safe," he said in a video posted on Telegram as he made his way back to Kyiv.

Russia maintaining a blockade of Odessa that has trapped grain supplies and threatens a global food crisis.

Russia's defence ministry said Sunday it launched missile strikes during the past 24 hours, with one attack on a top-level Ukrainian military meeting near the city of Dnipro killing "more than 50 generals and officers".

It said it also targeted a building housing Western-provided weapons in Mykolaiv, destroying Ukrainian artillery and armoured vehicles.

There was no independent verification of the claims.

Mykolaiv is a key target for Russia as it lies on the route to the strategic port of Odessa.

With Russia maintaining a blockade of Odessa that has trapped grain supplies and threatens a global food crisis, residents have turned their attention to rallying the home front effort.

"Every day, including the weekend, I come to make camouflage netting for the army," said Natalia Pinchenkova, 49, standing by a large Union flag, a show of thanks to Britain for its support for Ukraine.

Agence France-Presse