Ukraine's Security Service (SBU) said it has managed to strike the Crimean bridge with underwater explosives after a "month" operation.

SBU said its agents have "dig the bridge's support" with 1,100 kilograms of explosives that "severely damage" the bottom layer of the support.

The SBU added that the "first explosive device" was activated early Tuesday morning "without any civilian casualties." The information shared by the SBU cannot be verified immediately.

Russian media initially said the bridge had been temporarily closed but reopened at 10:00 local time (08:00 GMT).

However, later in the day, local authorities warned that the bridge was closed again.

Unconfirmed reports on social media say more explosions have occurred around the structure.

"We require personnel on the bridge and inspected areas to remain calm and follow the instructions of transport safety personnel," the official telegraph channel said in a statement.

Russia has not commented on Tuesday morning's attack, but Russian military bloggers speculated that underwater drones, rather than explosively, hit protective barriers.

SBU said its director, Lieutenant Vasyl Malyuk, personally oversees the operation and coordinates its plans.

In the telegram post, it quoted Malyuk as saying that Ukraine attacked the Crimean Bridge in 2022 and 2023, thus "continuing this tradition underwater."

"There are no illegal Russian facilities that have a place in our state's territory," Marik said.

“The Crimea Bridge is therefore an absolutely legitimate target, especially given the enemy’s use of it as a logistics artery to provide troops.”

The bridge - also known as the Kerch Bridge - was built by Russia after its invasion and annexation of the Crimean Peninsula in 2014. Russian President Vladimir Putin announced the bridge in 2018.

In Ukraine, this bridge is a disgusting symbol of Russian occupation. Moscow guards it carefully - it is an amazing achievement to do any attack on it whether it is using an underwater drone or explosives.

Tuesday's strike on the bridge came just 48 hours after Ukraine reached several goals across Russia, part of an action known as the "spider web."

Keefe said it smuggled more than 100 drones to Russia and managed to deliver them near the air base through unsuspecting van drivers.

Then, the drone flew out of the truck and attacked Russia's famous strategic bombers across the country.