'Heavy fighting' in Ukraine's southern offensive

STORY: This video uploaded to Youtube shows munitions being detonated in the Kherson region.

Ukraine has launched an offensive here to retake the south...

...though Reuters was unable to verify the exact location - or whether the explosions were Ukrainian or Russian.

The fighting comes after weeks of relative stalemate.

Late Monday evening, President Volodymir Zelenskiy urged Russian soldiers to flee for their lives -

while Russia responded by claiming it had repulsed the attack - and inflicted heavy losses on Kyiv's troops.

Meanwhile - the Zaporizhzhia nuclear power plant remains a hotspot in the conflict.

Inspectors from the U.N. nuclear watchdog agency arrived in Kyiv on Tuesday -

ahead of their much anticipated visit to the plant this week.

They'll be assessing any damage, as fighting is still being reported around the Zaporizhzhia facility.

It was captured by Russia in March, and both sides trade blame for shelling in the vicinity.

Russia says radiation levels around the plant are normal, for now.

It's unclear how successful Ukraine's offensive in the south has been so far.

Unverified reports on social media suggest its forces may have taken back some villages.

Britain, a close ally of Ukraine, says Kyiv has stepped up its artillery barrage across the southern front...

But that it's impossible to gauge the extent of its territorial advances.

Ukraine, now armed with sophisticated Western-supplied weapons - sees re-taking the region as crucial to stopping Russia from taking more territory to the west...

that could eventually cut off its access to the Black Sea.