A Russian railway bridge was damaged in an explosion in the region of Samara on the Volga river on Monday, Ukrainian military intelligence coy over wther it was involved.
"There are no deaths or injuries," the Russia FSB intelligence service in the Samara region told the state news agency TASS.
The area around the bridge in Chapayevsk was cordoned off. According to initial information, the cause of the blast was an explosive device.
Ukrainian military intelligence service HUR confirmed its knowledge of the explosion. Without taking direct responsibility, the HUR described the bridge as important military infrastructure.
Moscow has previously transported military lorries and explosives over the bridge by rail. Traffic on the line was temporarily suspended.
Chapayevsk is located around 1,000 kilometres from Ukraine, which was invaded by Russia more than two years ago. If Ukraine is involved, it would be one of the most daring attacks deep inside Russia during the war.
One of the major flashpoints of the conflict has been the Ukrainian nuclear power plant in Zaporizhzhya falling into Russian hands.
The head of the International Atomic Energy Agency (IAEA), Rafael Grossi, plans to hold talks with Russian President Vladimir Putin this week over the "precarious" situation at the power station.
Europe's largest nuclear plant is currently supplied with only a single power line for cooling nuclear material, Grossi said during a press conference in Vienna during an IAEA board of governors meeting.
The IAEA chief plans to leave for Russia on Tuesday.
Russian troops occupied the Zaporizhzhya nuclear power plant at the beginning of March 2022. Since then, nine of the original 10 lines that supplied the plant with electricity have failed due to the war.
An IAEA team is constantly on site to monitor the situation at the largely decommissioned plant, which is very close to the front line. The experts reported military activities near the plant this weekend.
"The physical integrity of the station continues to be at risk," said Grossi, who pushed a plan at the UN to prevent fighting at the plant.
The IAEA chief met Putin in October 2022 to negotiate the establishment of a security zone around the plant. Grossi's plan was never implemented, partly due to resistance from Ukraine.
In a recent report for the IAEA board of governors, Grossi complained that his team on site was not allowed to move freely around the facility to check that no weapons systems were stationed there.
He also pointed to the significant drop in staffing levels, delayed maintenance work and lack of spare parts under Russian management.
In another blow for Russia's industrial prestige, the manufacturer of Russia's latest Armata main battle tank said it is too expensive for use in the war against Ukraine.
"In terms of its functionality, it is far superior to existing tanks, but it is too expensive and therefore the army is unlikely to deploy it now," Sergey Chemezov, head of the state armaments holding Rostec, told the state news agency Ria Novosti.
The Armata T-14 was first presented to the public in 2015 at the annual military parade in Moscow. According to reports, the tank did not initially enter series production due to technical problems.
The Russian armed forces have since taken the Armata into service, said Chemezov, a close confidant of Russian President Vladimir Putin. However, the costs are too high for deployment in Ukraine.
"Today we need money to produce new tanks, new weapons, possibly cheaper ones," said Chemezov. It was therefore appropriate to buy cheaper T-90 tanks for the current conflict. The Armata was originally intended to replace the T-90.
