The Ukrainian military has said that Russian forces are stepping up their surveillance activities in apparent preparation for more missile attacks.

Ukrainian military officials said on Sunday that the Russian side is using drones to spy on Ukraine's military facilities. They warned that Russian forces are planning to strike targets including key infrastructure facilities.

On Saturday, Ukraine's defense minister Oleksii Reznikov said three military helicopters donated by Britain had arrived near the Black Sea in southern Ukraine.

Reznikov expressed his gratitude to Britain, tweeting, "It is a strong reinforcement for the Ukrainian Navy."

He added that the two countries will continue their cooperation and "secure the seas and lands across all of Europe."

A Ukrainian news agency said the helicopters will be used mainly for search and rescue operations.

Meanwhile, the chairperson of the lower house of the Russian parliament, Vyacheslav Volodin, condemned the Western countries' military support for Ukraine.

He posted on social media on Sunday that the West's deliveries of offensive weapons to Ukraine will lead to a "global catastrophe."