Ukrainian intelligence on Saturday admitted its role in the attack on the bridge of Crimea, which was annexed by Russia in 2014, seven months after the operation, which was described as qualitative and damaged part of the strategic bridge.

Ukrainian domestic intelligence chief Vasyil Maliuk said in an interview: "Since it is a supply route that we had to cut off on the enemy, appropriate measures were taken." He did not give more details about the operation.

In his interview with Ukrainian journalist Dmytro Komarov broadcast on YouTube, Maliuk explained that Ukraine had acted in accordance with the "traditions of war."

He also noted that since the beginning of the war more than 15 months ago, the Ukrainian domestic intelligence service has formed what it called "a special unit for sabotage on Ukrainian territory against the enemy."

Maliuk said Russian authorities were continuing to conduct what he called "fake investigations" into the bridge attack. More than 20 Russians suspected of involvement in the crime have been arrested.

The Crimean bridge attack took place on Oct. 8, a day after Russian President Vladimir Putin's seventieth birthday, who describes the construction of the bridge as one of his most important achievements.

The bridge was detonated by a truck bomb that partially destroyed it, igniting 7 fuel tanks in a train that was traveling across the bridge parallel to the explosive part, without damaging the navigation arc under the bridge, and Russian media estimated the extent of the damage at about $ 10 million.

Three people were killed in the blast, including the driver of the truck along with a man and a woman who were in a car near the blast.

Although Kiev flatly declined to comment on the incident at the time, in December Maliuk suggested that his agency had something to do with the attack.

The bridge to Crimea, which was closed for days before being repaired, is a vital route for Russian military supplies in the war with Ukraine and is the longest in Europe at 19 kilometres linking the Russian mainland and the peninsula.

Maliuk noted that the October drone attacks on Russian fleet warships in the Black Sea in the Sevastopol Gulf were also part of a special operation of Ukrainian internal intelligence with the Ukrainian armed forces.