Britain's defense ministry says Russia has used a massive amount of antitank mines to slow the advance of Ukraine's forces in the country's south.

The ministry said on Tuesday that in recent weeks, Russia has prioritized and refined tactics aimed at slowing Ukrainian armored counteroffensive operations in the south. It also said Russia attempted to strike Ukrainian armored vehicles with drones, attack helicopters and artillery.

But the ministry added that although Russia has achieved some success with this approach in the early stages of the counteroffensive, its forces continue to suffer from key weaknesses, especially overstretched units and an artillery shortage.

On Monday, Ukraine's deputy defense minister Hanna Maliar said on social media that fighting near the key eastern city of Bakhmut had intensified.

Ukraine launched a massive counteroffensive against Russian forces in early June, but observers say its progress has been slower than expected.

Meanwhile, Russia's defense ministry said five drones reached Moscow and its outskirts on Tuesday, in what it called an attempted terrorist attack by Ukraine. It also said there were no casualties or damage.

Local authorities say flight operations were temporarily limited at Vnukovo Airport in southwestern Moscow.

Russia has been on high alert since drones reached the capital on May 30, damaging residential buildings.