Russia's oil refining capacity that was shut down by drone attacks has reached 14% of total, Reuters calculations showed on Tuesday.

Ukraine has stepped up attacks on Russian oil facilities since the start of the year to diminish Moscow's military capabilities, while Russia has also been mounting massive attacks on Ukraine's energy infrastructure.

The outages roiled global energy markets and buoyed oil prices.

Reuters calculation showed that combined capacity of primary oil refining units, knocked out by drones, now stands at 124,580 metric tons per day, or 900,000 barrels per day.

Among top refineries crippled by drone attacks are Lukoil's Norsi and Volgograd, as well as Rosneft -owned Kuibyshev, Tuapse and Ryazan plants.

Primary refining capacity for gasoline and diesel production for the domestic market idled by drones, stands at 86,870 tons per day, or 9.8% of Russia's total primary oil refining capacity.

(Reporting by Reuters Editing by Tomasz Janowski