UN nuclear inspectors have set off for Ukraine's Zaporizhzhia nuclear power plant after weeks of shelling nearby sparked fears of a Fukushima-style radiation disaster, with tensions rising between Kyiv and Moscow over the visit.
A Reuters reporter travelling in a convoy with the team from the International Atomic Energy Agency (IAEA) from Kyiv, the Ukrainian capital, said it was likely the inspectors would overnight in the nearby city of Zaporizhzhia before visiting the plant, which is on territory controlled by Russia, on Thursday.
Russian-installed officials in the area suggested the visit might last only one day, while IAEA and Ukrainian officials suggested it would last longer.
"We are now finally moving after six months of strenuous efforts," IAEA chief Rafael Grossi told reporters before the convoy set off, adding that the mission planned to spend "a few days" at the site.
"We have a very important task there to perform - to assess the real situation there, to help stabilise the situation as much as we can. We are going to a war zone, we are going to occupied territory and this requires explicit guarantees, not only from the Russian Federation but also from Ukraine. We have been able to secure that," said Grossi.
Russia captured the plant, Europe's largest, in early March.
A Russian military force has been at the plant ever since as has most of the facility's Ukrainian workforce who have toiled to keep the facility, which traditionally supplied Ukraine with 20 per cent of its electricity needs, running.
Ukraine and Russia have accused each other of endangering the plant's safety with artillery or drone strikes.
Kyiv says Russia has been using the plant as a shield to strike towns and cities, knowing it will be hard for Ukraine to return fire. It has also accused Russian forces of shelling the plant.
"The situation at the Zaporizhzhia nuclear power plant and in Enerhodar and surrounding areas remains extremely dangerous," Ukrainian President Zelenskiy said on Tuesday. "The risk of a radiation disaster due to Russian actions does not decrease for an hour."
Moscow has denied Ukrainian assertions of reckless behaviour, questioning why it would shell a facility where its own troops are garrisoned.
Moscow has in turn accused the Ukrainians of shelling the plant to try to generate international outrage that Kyiv hopes will result in a demilitarised zone.
Grossi said the IAEA hoped to set up a permanent mission at the plant and that one of his priorities was to talk to the Ukrainian technicians running it.
It was unclear if Grossi's desire to spend "a few days" at the plant would be possible however, after Yevgeny Balitsky, head of the Russian-installed administration in the area, told the Interfax news agency that the IAEA inspectors "must see the work of the station in one day".
Zelenskiy in a late night address on Tuesday said Ukrainian forces were attacking Russian positions in Ukraine along the entire frontline after Kyiv announced on Monday it had launched an offensive to try to retake the south.
Zelenskiy said his forces were also on the offensive in the east.
"Active military engagement is now happening along the whole front line: in the south, in the Kharkiv region, in Donbas," Zelenskiy said.
Russia captured large tracts of southern Ukraine near the Black Sea coast in the early weeks of the six-month-old war, including in the Kherson region, which lies north of the Russian-annexed Crimean Peninsula.
Ukraine sees recapturing the region as crucial to prevent Russian attempts to seize more territory further west that could eventually cut off its access to the Black Sea.
Britain, an ally of Ukraine, said Ukrainian formations in the south had pushed Russian front-line forces back some distance in places, exploiting relatively thin Russian defences.
Russia's defence ministry said its troops had routed Ukrainian forces.