The Russian Submarine Rostov-on-Don was attacked at the port of Sevastopol on August 2 - CNN reported, citing the General Staff of the Ukrainian Armed Forces in a statement on August 3.
The General Staff said the ship sank on the spot, but did not provide further evidence.
The Ukrainian Defense Ministry praised the attack, writing in a social media post that "a Russian Submarine sank to the bottom of the Black Sea" after being attacked at the port of Sevastopol. The consequences of the attack were that the Submarine sank. Do a very good job, warriors".
Crimea was annexed by Russia in 2014. Since the Russia-Ukraine conflict broke out more than two years ago, the area has been repeatedly attacked by Kiev forces.
CNN could not independently verify the above statement of Ukraine and the Russian Ministry of Defense has not commented.
Sevastopol Governor Mikhail Razvozhayev said the Submarine Defensive Drills took place on August 3 and "everything was peaceful in the city".
In a post on August 3, Russian military blogger Boris Rozhin wrote that the ship repair plant in Sevastopol, where the tankers were anchored, appeared to have been attacked.
Commissioned in 2014, the Rostov-on-Don is a Kilo II-class Submarine, 73.8 meters long, carrying 52 crew. With a dipping capacity of 3,100 tons, the electric-diesel ship could carry a kalibr cruise missile.
The destruction of Russian weapons equipped with kalibr missiles is an important part of Ukraine's military strategy as Russia has used kalibr and similar missiles to attack Ukraine's critical infrastructure - Cedric Leighton, a military analyst at CNN, said.
Ukraine has previously targeted the Rostov-on-Don Submarine. The Ukrainian General Staff said the Submarine was "seriously damaged" in a Ukrainian missile attack in September 2023.
Following the attack, open-source intelligence photos, including those cited by the British Ministry of National Defense, showed what the ministry called " catastrophic damage".
But the Ukrainian General Staff said the Rostov-on-Don ship had been repaired and had recently been tested in the Sevastopol port area.
The Russian Navy's biggest loss in the conflict was the sinking of a missile cruiser leading to Moscow in April 2022.
Last October, satellite imagery showed Russia had moved several naval vessels out of Sevastopol following a series of Ukrainian attacks.
In addition to the attack on the Submarine, the Ukrainian forces also said that they had seriously destroyed four Russian S-400 anti-aircraft missile launchers.
Leighton said the destruction of the S-400 could help open up the sky over Crimea for more Ukrainian fighter jets to attack Russian targets.
In another development, head of the General Intelligence Service of Ukraine (GUR) Kirill Budanov said Kiev is planning to destroy the Crimea bridge in the next few months or by the end of this year - RT reported.
Senior Ukrainian officials, including President Volodymyr Zelensky, have justified Kiev's continuous efforts to destroy the bridge between the Crimean peninsula and Krasnodar region, claiming that it has significant logistical value for the Russian army.
The bridge was completed in 2020. Since the escalation of the Ukrainian conflict in 2022, Kiev has made several efforts to destroy the bridge, including the use of long-range missiles supplied by the West, Navy drones packed with explosives, as well as explosives smuggled into vehicles.
Despite Ukraine's efforts, the Crimea bridge has only been damaged twice.
