(Reuters) - The head of the International Atomic Energy Agency raised grave concern about shelling at a nuclear power plant in Ukraine, as its military said Russian forces had attacked dozens of front-line towns.
Since Russia invaded Ukraine on Feb. 24 in what President Vladimir Putin termed a "special military operation", the conflict has settled into a war of attrition fought largely in Ukraine's east and south.
But the fighting over the Zaporizhzhia nuclear plant in the south, captured by Russian forces in the opening stage of the war but still run by Ukrainian technicians, has raised the prospect of a wider disaster.
"I'm extremely concerned by the shelling yesterday at Europe's largest nuclear power plant, which underlines the very real risk of a nuclear disaster," IAEA Director General Rafael Mariano Grossi said in a statement.
Both sides have accused each other of engaging in "nuclear terrorism".
Ukraine's state nuclear power company Energoatom blamed Russia for the damage while Russia's defence ministry accused Ukrainian forces of shelling the plant.
The United States has accused Russia of using it as a "nuclear shield" while Russia's defence ministry said damage to the plant had only been avoided thanks to the "skilful, competent and effective actions" of its units.
Grossi, who leads the United Nation's nuclear watchdog, urged all sides to exercise the "utmost restraint".
Shells hit a high-voltage power line on Friday at the facility, prompting its operators to disconnect a reactor despite no radioactive leak being detected.
While the world's attention was focussed on the nuclear plant, the war was grinding on in the east and south.
Russia is trying to gain control of the largely Russian-speaking Donbas region in the east, comprised of Luhansk and Donetsk provinces, where pro-Moscow separatists seized territory after the Kremlin annexed Crimea to the south in 2014.
Ukraine's military said late on Saturday that Russian forces had shelled dozens of front-line towns and were trying to attack in six different areas in the Donetsk region, all of which failed to gain any territory and were held back by Ukrainian forces.
Reuters could not verify either side's assertions about battlefield developments.
Ukraine's President Volodymyr Zelenskiy said on Saturday said that over the past week its forces had "achieved powerful results" in destroying Russia's logistics supplies and rear bases.
"Every strike on the enemy's ammunition depots, on their command posts, and on accumulations of Russian equipment saves the lives of all of us, the lives of Ukrainian military and civilians," he said in a late-night video address.
On Saturday, a foreign-flagged ship arrived in Ukraine on Saturday for the first time since the war started, to load up with grain, Ukrainian Infrastructure Minister Oleksandr Kubrakov said.
Zelenskiy welcomed the resumption of exports though he said risks remained.