Ukraine claimed that it carried out a naval drone attack targeting a Russian warship in the Black Sea port of Novorissiysk on Friday.
The attack was confirmed by Moscow, but its Defense Ministry claimed no damage had been caused, despite videos and photos showing the contrary.
The strike on the ship Olenegorski Gornyak, meaning Olenegorsk Miner, was a great loss for the Russian fleet, HUR military intelligence spokesman Andriy Yusov told Ukrainian state TV's Russian-language foreign channel Freedom.
"For Ukraine, this is good and just news," he said on Friday. "This will continue."
Yusov stressed that these landing ships were a strategic risk for Ukraine. The port city of Novorossiysk, located in the Krasnodar region, is a base of the Russian Black Sea Fleet and an important location for oil exports.
Russia reportedly uses this type of ship to transport troops and material to the Russian-occupied Crimea peninsula, which it annexed in 2014.
An earlier video of the operation showed a naval drone belonging to Ukraine's SBU intelligence service, loaded with 450 kilograms of explosives, attacking a Russian ship. The ship reportedly had a crew of about 100, according to several media outlets which cited a Ukrainian informant.
The video released on Twitter shows the attack from the drone's perspective until it collides with the ship.
It was reportedly a joint operation between the SBU and Ukrainian Navy, media in Kyiv further reported.
Ukraine does not have a strong navy. However, last year it sank the flagship of the Russian Black Sea Fleet, Moskva. More recently, Kyiv has also used unmanned explosive boats against Russian targets.
Later images showed the Olenegorski Gornyak, commissioned in 1976, lying tilted on its side in Novorossiysk Bay.
The Caspian Pipeline Consortium, which loads oil in Novorossiysk, said earlier that shipping had been temporarily suspended.
Yusov added that the incident represented a "tragedy" for Russian propaganda. The Russian Defense Ministry had earlier claimed that the attack had been repelled, but videos show the drone hitting the ship and images show it tipped on its side.
Even pro-war Russian military bloggers published photos and videos of the ship on its side and wrote about the damage.
Mykhailo Podolyak, the adviser to the Ukrainian presidential office in Kyiv, said on Friday that Ukrainian naval drones would completely change "the rules of the game."
The Russian naval presence in the Black Sea "will be put to an end," he said. In the future, he added, Ukraine would ensure "freedom and security in the Black Sea for world trade."
More than 17 months after the start of Russia's unprovoked full-scale invasion of Ukraine, the situation in the Black Sea is particularly tense after Moscow canceled an agreement to allow for the export of Ukrainian grain a few weeks ago.
Since then, the Russian army has repeatedly bombarded Ukrainian coastal regions, severely damaging port infrastructure and food storage facilities.
Moreover, the British Ministry of Defense said Friday that Russia is taking risks to prevent grain exports from Ukraine.
Russia recently used Iranian kamikaze drones to target sites only 200 meters from the Romanian border, where NATO territory starts. "Russia has evolved its risk appetite for conducting strikes near NATO territory," said British intelligence experts.
The aim of these attacks is to force international shipping to stop trade through Ukrainian Danube ports, they added.
A grain silo in the port of Izmail on the Danube was destroyed recently.
Russia's Defence Ministry meanwhile posted a video on Friday of Defence Minister Sergei Shoigu visiting Russian troops in Ukraine. The video shows him in a helicopter speaking to other officers.
He is reportedly said to have visited a Russian army group known as "Centre" headed by Commander Andrei Mordvichev.
It was not known exactly where and when the footage was taken. The ministry had published footage of Shoigu's travels before, which were later analyzed by experts and said to have happened earlier.
On the ground, Kyiv's forces have made further gains in the territory near the Russian-controlled city of Bakhmut, according to the Ukrainian Defence Ministry.
"On the southern flank, despite heavy artillery fire and mines, our forces continue to advance step by step," Ukrainian Deputy Defense Minister Hanna Maliar said on Telegram on Friday.
The General Staff reports suggest that the Klishchiivka village, south of Bakhmut, is no longer fully under Russian control.
Ukrainian forces also repelled Russian attacks north of Bakhmut and in the areas of Kupiansk, Lyman and Svatove at the borders between the eastern Ukrainian regions of Luhansk, Kharkiv and Donetsk.
"Heavy fighting is taking place," Maliar said. The Russian military is aiming to reclaim areas lost last year. The Ukrainian army, she added, was continuing its advance on the southern Ukrainian front lines despite "fierce resistance."
Mines and concrete fortifications were reported.