A drone struck the primary oil refining unit (CDU-7) at Russia's Taneco oil refinery, one of the country's biggest, on Tuesday, according to Reuters analysis of images showing the impact of the attack.

The unit accounts for around a half of the plant's total annual production capacity of more than 17 million tons (340,000 barrels per day).

Earlier on Tuesday, Russian officials had said Russia repelled the drone attack on the refinery, which is nearly 1,300 km (800 miles) from Ukraine. (Reporting by Reuters)