Russian President Vladimir Putin said on Friday that Moscow was conducting its nearly eight-month invasion of Ukraine correctly, despite his forces' early failure to topple Kyiv and a string of recent embarrassing battlefield defeats.

But his comments came hours after Kremlin-installed officials in Ukraine's southern region of Kherson urged residents to leave, pointing to nearing Ukrainian artillery and as Kyiv announced its forces were pushing closer towards the region's main city.

And on Thursday Moscow also hinted at the potentially wide extent of the damage dealt to the Crimea bridge, saying it could take many months to complete repairs after a recent blast rocked the key supply link between Russia and the annexed Crimean peninsula.

"What is happening today is not pleasant. But all the same, (if Russia hadn't attacked on February) we would have been in the same situation, only the conditions would have been worse for us," Putin told reporters after a summit in the capital of Kazakhstan.

"So we're doing everything right," he insisted.

Nearly eight months into Moscow's war, Ukraine's emboldened military, which is clawing back territory in the east as well as in the south, was celebrating Defender's Day. Meanwhile a United Nations envoy alleged Russian forces were using rape as a weapon.

Putin described the explosion on the Crimea bridge on Saturday as a "terrorist" act and in retaliation battered Ukraine for two days with missiles that hit energy facilities and caused blackouts and disruption to water supplies.

Speaking to reporters on Thursday, he said that "for now" he saw no need to continue the massive salvo of missiles that hit cities across Ukraine -- several far from the front line -- and left at least 20 civilians dead. He explained the Russian military had other objectives.

'The world is with us'

"Our aim is not to destroy Ukraine," Putin added.

The Crimea bridge is logistically crucial for Moscow. It is a vital transport link for moving military equipment to Russian soldiers fighting in Ukraine.

But it is also symbolically important to Putin, who inaugurated the bridge in 2018 several years after he annexed the peninsula from Ukraine to a chorus of Western condemnation.

The missile barrage on Monday and Tuesday, he said, was direct retaliation for the blast.

Russia's cabinet, in a decree signed by Prime Minister Mikhail Mishustin, ordered the company tasked with the "design and restoration of destroyed elements of ... the Crimean Bridge" to complete the work by July 1, 2023.

That date gives an indication of the extent of the damage caused by the explosion at the bridge because Russian officials have otherwise been circumspect about the lasting impact of the incident.

They did however say hours after the blast -- which they blamed on Ukraine special forces -- that both road and rail traffic had been restored.

In Kyiv on Friday, President Volodymyr Zelensky vowed, during events marking the country's first Defender's Day celebrations, that Ukrainian troops would be victorious over Russian forces

He also laid a wreath at a memorial for soldiers killed since 2014, when Kremlin-backed separatists wrested control of parts of two eastern regions. In February this year, the separatists appealed for Russia to intervene.

"The world is with us, more than ever. This makes us stronger than ever in history," Zelensky added in reference to unprecedented Western aid.

Ukrainian forces mounted a counter-offensive in the south towards the end of the summer and have been pushing closer and closer to the main city in the Kherson region, also called Kherson.

On Friday, the Moscow-installed authorities in the region renewed a call for residents to temporarily leave, with reports that Ukrainian forces had been gaining ground near Kherson.

Advance on Kherson

"The bombardments of the Kherson region are dangerous for civilians," Kirill Stremousov, the deputy head of the pro-Russian regional administration said. He urged residents to take a trip for "rest and recreation" elsewhere.

But in the east, pro-Russian forces said they were closing in on the industrial city of Bakhmut after they reported the capture of two villages on the city's outskirts this week.

An official of the so-called Lugansk People's Republic, a pro-Kremlin breakaway region in east Ukraine, said "active hostilities were underway" within Bakhmut.

"Our forces are confidently marching and liberating this settlement," the official, Andriy Marochko, was quoted as saying by Russia's state-run TASS news agency.

Also this week, UN envoy Pramila Patten told AFP in an interview that rapes and sexual assaults attributed to Moscow's forces in Ukraine were part of a Russian "military strategy" and a "deliberate tactic to dehumanize the victims".

"When you hear women testify about Russian soldiers equipped with Viagra, it's clearly a military strategy," the UN special representative on sexual violence said on Thursday. "It is clearly a deliberate tactic to dehumanise the victims."

© Agence France-Presse