Authorities say they have seized cargo comprising of home-made explosives as Ukrainian drones hit deep inside Russia.

The seizure took place on Tuesday, following an inspection of cargo in the northwestern Pskov region near the Latvian border, the Federal Security Service (FSB) said in a statement.

There was no immediate comment by Ukraine, which has been fighting off a Russian invasion since February 2022.

The FSB said the cargo had passed through Romania, Hungary, Slovakia, Poland, Lithuania and Latvia, and comprised 70 kilos (154 pounds) of home-made explosives and explosive devices “hidden in icons and ready for use”.

One person was arrested, it continued, adding that it would seek to track down all those involved, including foreigners, who would then face legal proceedings in Russia.

Drones hit targets deep into Russia

Separately on Tuesday, Russian officials said Ukrainian drones had struck sites in Tatarstan, a highly industrialised area southeast of Moscow and about 1,300km (800 miles) from the front lines.

One of the attacks, the deepest inside Russian territory since the war began, targeted Russia’s third largest oil refinery, which has an annual production capacity of more than 17 million tons (340,000 barrels per day)

A fire broke out at Tatneft’s Taneco refinery that was extinguished within 20 minutes, the state RIA news agency said, adding that production had not been disrupted.

Pictures from the scene indicated the drone hit the primary refining unit, CDU-7, at the Taneco refinery. The unit accounts for about half of the plant’s total annual production capacity.

“A drone attack was carried out on one of the enterprises in Nizhnekamsk,” Ramil Mullin, the mayor of Nizhnekamsk, said. “There are no casualties or serious damage.”

Tatarstan head Rustam Minnikhanov also said industrial zones in the cities of Nizhnekamsk and Yelabuga had been targeted, adding that the “technological process” of the companies concerned had not been destroyed.

At least six people were injured in the attack on a site in Yelabuga, the state-run TASS news agency reported, citing local emergency services.

Videos on social media showed an aircraft-style drone flying into a two-storey building at a business park outside the city before exploding, sending a fireball into the air.

More Russian attacks on energy sites

Meanwhile, Ukraine’s military said Russian drones targeted energy infrastructure in overnight attacks on Ukraine’s central Dnipropetrovsk and Kirovohrad regions, hitting an energy facility in the latter.

Nine drones were shot down over Dnipropetrovsk region where debris caused two fires in the regional capital of Dnipro, the governor said in a statement on Telegram, adding they had both been put out.

However, a drone hit a high voltage substation in Kirovohrad region, causing a fire there, the Ukrenergo grid operator wrote on Telegram. The governor said no casualties had been reported.

Air defences were able to down nine out of 10 of the incoming Russian drones, the General Staff said.

Russia has escalated its attacks on Ukrainian energy infrastructure in recent days, causing significant damage in several regions.