Ukrainian missile strikes on rail crossings in Crimean last month caused "significant temporary disruption" to Russian forces on the peninsula, the United Kingdom's Ministry of Defense concluded in an intelligence update on Thursday.

The ministry said the May 29 attack on the two rail ferries on the Crimean side of the Kerch Strait crossing knocked them out of operation.

"These rail ferries almost certainly provided the primary means of rail transportation for Russian fuel and ammunition train loads to Crimea due to stringent security measures employed on the Kerch Bridge," Defense Intelligence said on X.

The assessment said Moscow will "almost certainly" be forced to replace the ferry service, "likely impacting its wider maritime logistics operations, or risk relaxing its procedures by using the rail bridge to transit fuel and explosive stores."

"The Ukrainian strike on the ferry crossings and a subsequent attack on a nearby fuel depot, highlights again the vulnerability of the Strait to Ukrainian interdiction, despite Russia's significant investment in security and air defense," the statement said.

Ukrainian forces have been stepping up attacks against Russia after getting the nod from the Biden administration to go after military targets inside the country using U.S.-made weapons.

Ukraine fired dozens of precision-guided arms at Russian troop placements, artillery systems and the bridge, using M42 missiles that are fired by track-mounted M270 rocket launcher and the wheel-mounted HIMARS rocket launcher.