By Natalia Zinets
KYIV (Reuters) -Ukrainian and Russian-installed officials reported shelling near the Zaporizhzhia nuclear plant in southern Ukraine on Monday, with both sides blaming each other days after the world nuclear watchdog warned of disaster if the fighting does not stop.
Russia and Ukraine have traded accusations this month of shelling near the plant, which dominates the south bank of a vast reservoir on the Dnipro River, amid fears of a nuclear catastrophe.
Ukrainian President Volodymyr Zelenskiy has warned Russian soldiers who attack Europe's largest nuclear power station or use it as a base to shoot from that they will become a "special target".
The plant is in the now Russian-controlled city of Enerhodar.
Yevhen Yevtushenko, head of the administration of the Nikopol district, which lies across the river from Enerhodar, accused Russian forces of shelling the city.
Vladimir Rogov, a Russia-installed official in Enerhodar, said that over the past two hours about 25 heavy artillery strikes from U.S.-made M777 howitzers had hit near the nuclear plant and residential areas.
Russia's Interfax news agency, quoting the press service of Enerhodar's Russian-appointed administration, said Ukrainian forces opened fire, with blasts near the power plant.
The International Atomic Energy Agency (IAEA), which is seeking access to the plant, has warned of possible disaster. Nuclear experts fear fighting might damage the plant's spent fuel pools or reactors.
"The Russians think they can force the world to comply with their conditions by shelling the Zaporizhzhia NPP (nuclear power plant)," Andriy Yermak, chief of the Ukrainian presidential staff, wrote on Twitter. "This will not happen. Instead, our military will punish them by hard hitting with precision on pain points."
U.N. Secretary-General Antonio Guterres has called for the establishment of a demilitarised zone around Zaporizhzhia. The United Nations has the logistics and security capacity to support an IAEA visit if both Russia and Ukraine agree, U.N. spokesman Stephane Dujarric said.
Russian Defence Minister Sergei Shoigu held a phone call with Guterres to discuss conditions for the safe functioning of the plant, the ministry said.
A spokeswoman for Russia's foreign ministry said it would do all it could to allow IAEA specialists to visit.
"In close cooperation with the agency and its leadership, we will do everything necessary for the IAEA specialists to be at the station and give a truthful assessment of the destructive actions of the Ukrainian side," spokeswoman Maria Zakharova said.
Ukraine, where parliament on Monday extended martial law for a further three months, has said for weeks it is planning a counteroffensive to recapture Zaporizhzhia and neighbouring Kherson province, the largest part of the territory Russia seized after its Feb. 24 invasion and still holds.
Ukrainian forces reported heavy Russian shelling and attempts to advance on several towns in the eastern region of Donetsk that has become a key focus of the near six-month-old war, but said they had repelled many of the attacks.
The General Staff of Ukraine's armed forces also reported Russian shelling of more than a dozen towns on the southern front - particularly the Kherson region, mainly held by Russian forces but where Ukrainian troops are steadily retaking territory.
A Russian-backed separatist court in Donetsk charged five foreign nationals captured fighting with Ukrainian forces with being mercenaries, saying three could face the death penalty, Russian media reported.
Russia calls its invasion of Ukraine a "special military operation" to demilitarise its smaller neighbour and protect Russian-speaking communities. Ukraine and Western backers accuse Moscow of waging an imperial-style war of conquest.
The conflict has pushed Moscow-Washington relations to a low point, with Russia warning it may sever them.
Russian President Vladimir Putin said Moscow was ready to offer modern weapons to its allies, using a speech at an arms show near Moscow to boast of Russia's advanced weapons capabilities.
"(We) are ready to offer our allies the most modern types of weapons, from small arms to armoured vehicles and artillery to combat aviation and unmanned aerial vehicles," Putin said at the opening ceremony of the "Army-2022" forum.
"Almost all of them have been used more than once in real combat operations."
Putin's military has performed worse than expected in Ukraine. It has been beaten back from Ukraine's two biggest cities and is making slow headway, at heavy cost, in the east of the country, making the war an unconvincing showcase for Russia's arms industry.
(Reporting by Natalia Zinets in Kyiv, Yoruk Isik and Ece Toksabay in Istanbul, Andrea Shalal in Yuzhne, Maya Gebeily in Beirut and Jonathan Saul in London, and Reuters bureaux; Writing by Lincoln Feast and Nick Macfie; Editing by Mark Heinrich, Alex Richardson and Philippa Fletcher