Ukraine continues to cripple Russia's energy sector by hitting numerous oil refineries, depots, chemical plants, and more with drones.

Ukrainian drones struck deep inside Russia in an overnight attack targeting an oil facility serving a military airfield in the city of Engels, nearly 400 miles from the border, Ukraine’s military said Wednesday.

Ukraine launched its "most massive" attack against Russian military and industrial facilities in a range of up to 1,100 kilometers (620 miles) overnight on Jan. 14, the General Staff of Ukraine’s Armed Forces reported.

Ukraine launched waves of long-range strikes, including its ATACMS and Storm Shadow missiles, at targets inside Russia.

Europe warns its airlines to stay away through next summer, as Ukraine turns skies of western Russia into a battlefield.

While air raid sirens during visits by foreign leaders have sounded before, it is rare for air defenses to actually have to fight off attacking drones.

The Russian Defense Ministry said that Ukraine launched six ATACMS missiles overnight at the Bryansk region, but that all of them were downed by air defenses. The ministry also said that 146 Ukrainian drones had been shot down outside the conflict zone over the last day.

Located in Saratov Oblast, over 750 kilometers from the Ukrainian border, Engels airbase is home to Russian heavy bombers.

A Russian strike killed four people in the Ukrainian capital, Kyiv, city officials said on Saturday, in what the country's foreign minister called a "heinous" attack with ballistic missiles.

A Ukrainian drone attack on Friday sparked a fire at an industrial site in Russia some 170 kilometres (105 miles) from the border, authorities said.

Russia claimed it damaged ground infrastructure of one of the largest natural gas storage sites in Ukraine's Lviv region during a series of attacks on the country's energy sector.