Ukraine has intensified its drone attacks against Russian oil and oil products facilities in south and central Russia after a near six-month pause ended in early July when Russia targeted Ukrainian state company Naftogaz's gas production operations.

Early on Sunday a massive oil depot fire was raging near Russia's Black Sea resort of Sochi - blamed by the Russian authorities on a Ukrainian drone attack. Sochi's airport in the same area - Adler district - suspended flights.

An overnight Ukrainian drone attack on an oil depot near Russia's Black Sea resort of Sochi sparked a major fire, Russian officials have said, as the two countries traded strikes.