Russian President Vladimir Putin surveyed the drills carried out by his nuclear-capable forces as Moscow persisted in claiming, without offering evidence, that Kyiv was developing a "dirty bomb".

On Monday the Russian foreign ministry posted photographs of ostensible nuclear materials on social media it said depicted "Ukraine's capacities to create the 'dirty bomb.'"

But on Wednesday Slovenia said the photo came from its own nuclear waste management agency and dated to 2010.

According to Dragan Barbutovski, an advisor of Slovenian Prime Minister Robert Golob, it depicted smoke detectors.

Artillery rains

Ukrainian troops are holding out against repeated attacks by Russian forces in two eastern towns while those on the southern front are poised to battle for the strategic Kherson region, which Russia appears to be reinforcing.

Ukrainian President Volodymyr Zelensky said in a Wednesday evening video address that there would be good news from the front but he gave no details.

He did not mention what was happening in Kherson in the south, which officials and military analysts have predicted will be one of the most consequential battles of the war since Russia invaded Ukraine eight months ago.

The most severe fighting in eastern Ukraine was taking place near Avdiivka, outside Donetsk and Bakhmut, Zelensky said.

"This is where the craziness of the Russian command is most evident. Day after day, for months, they are driving people to their deaths there, concentrating the highest level of artillery strikes," he said.

Russian forces have repeatedly tried to seize Bakhmut, which sits on a main road leading to the Ukrainian-held cities of Sloviansk and Kramatorsk.

The looming battle for Kherson city at the mouth of the Dnipro River will determine whether Ukraine can loosen Russia's grip on the south.

The Russian-appointed Kherson regional government said it had rebased to the left bank of the Dnipro, Russia's RIA news agency reported, as forces braced for an increase in fighting.

Submarine missile launch

Western officials downplayed the Kremlin's war games, a regular event for which Moscow gave foreign counterparts advance warning.

"Under the leadership of [...] Vladimir Putin, a training session was held with ground, sea and air strategic deterrence forces, during which practical launches of ballistic and cruise missiles took place," the Kremlin said in a statement.

Russian state-run media ran footage of a submarine crew preparing the launch of a Sineva ballistic missile from the Barents Sea in the Arctic.

The drills also included launching test missiles from the Kamchatka peninsula in the Russian Far East.

In calls to Chinese and Indian correspondents, Russia's Defense Minister Sergei Shoigu continued to press his allegations that Ukraine planned to detonate "dirty bomb" -- a crude, small weapon filled with radioactive, biological or chemical materials -- which it would blame on Russia.

Indian Defense Minister Rajnath Singh said that in his call with Shoigu, he "pointed out that the nuclear option should not be resorted to by any side as the prospect of the usage of nuclear or radiological weapons goes against the basic tenets of humanity."