Russian oil company Bashneft, part of state-controlled giant Rosneft, has installed metal mesh at its refineries to protect them from drone attacks from Ukraine, Russian media reported on Friday, quoting Radiy Khabirov, the head of the Bashkortostan region where Bashneft is based.

“We don’t stop there. There are a number of solutions there, which I won’t talk about yet. They are classified. But believe me, we worry about this very much,” the Bashinform agency quoted Khabirov as saying.

This year, Ukraine has intensified attacks on oil refineries in Russia, which have reduced Russian refining capacity, and which, reportedly, have the White House concerned about rising international prices.

The United States has repeatedly urged Ukraine to halt its drone attacks on Russian oil refineries due to Washington’s assessment that the strikes could lead to Russian retaliation and push up global oil prices, the Financial Times reported last month, citing sources familiar with the exchange.

The drone attacks from Ukraine on Russian refineries could disrupt fuel markets globally, the International Energy Agency (IEA) said last week, estimating that up to 600,000 barrels per day (bpd) of Russia’s refinery capacity could be offline in the second quarter.

Russia has brought back online some oil refining units in recent weeks, reducing the capacity taken offline by Ukrainian drone hits to around 10%, from 14% at the end of March, calculations by sources showed earlier this week.

The refining capacity in Russia that is currently offline due to drone attacks is now estimated by Reuters at around 660,000 barrels per day (bpd), compared to 907,000 bpd offline at the end of March.

Still, maintenance and other outages at Russia’s refineries will actually raise the refining capacity that will be offline this month compared to March, according to Reuters’s data and calculations.

Russia said in early April it could repair all damaged units within two months. Russia’s Energy Minister Nikolai Shulginov has said that all damaged refineries in the country would be restarted by the beginning of June.