* U.N. chief met Zelenskiy, Turkey's Erdogan in Lviv
* Moscow rejects calls for demilitarised zone around plant
* Fresh blasts near Russian airbase in Crimea
By Natalia Zinets and Andrea Shalal
KYIV/LVIV, Ukraine, Aug 18 (Reuters) - The U.N. chief and the presidents of Turkey and Ukraine on Thursday discussed ways to end Kyiv's conflict with Russia and secure Europe's largest nuclear power station, which has come under shelling at the front lines.
Speaking with reporters after talks in Ukraine, U.N. Secretary-General Antonio Guterres said he was gravely concerned by the situation at the Zaporizhzhia nuclear plant and called for military equipment and personnel to be withdrawn.
After talks in the western Ukrainian city of Lviv, Turkey's President Tayyip Erdogan said he, Guterres and Ukrainian President Volodymyr Zelenskiy discussed building on recent positive atmosphere to revive peace negotiations with Russia that took place in Istanbul in March.
In a deal brokered by the U.N. and Turkey, the two sides recently reached an agreement for Russian to lift a blockade of Ukrainian grain shipments, and exports have started to resume.
NATO member Turkey has maintained good relations with Russia, an important trade partner, and sought to mediate in the six-month-old conflict.
"Personally, I maintain my belief that the war will ultimately end at the negotiating table. Mr Zelenskiy and Mr Guterres have the same opinion in this regard," Erdogan said.
There was no immediate comment from Moscow.
Meanwhile, 17 people were killed and 42 injured in two separate Russian attacks on the major northeastern Ukrainian city of Kharkiv, the regional governor said on Thursday.
Three civilians were killed and 17 wounded in a pre-dawn rocket strike on Thursday, the local emergency service said. That followed a Russian attack on Kharkiv on Wednesday, in which the emergency service initially said 12 people were killed.
Also on Thursday, at least four explosions hit near a major Russian military airport on the Moscow-controlled Crimean peninsula, three local sources said. Ukraine has hinted it orchestrated other blasts over the last 10 days at other Russian installations in Crimea.
The sources said Thursday's explosions were near Russia's Belbek military airport, north of the Black Sea fleet's headquarters in Sevastopol.
Sevastopol governor Mikhail Razvozhayev, writing on Telegram, said Russian anti-aircraft forces downed a Ukrainian drone and no damage occurred.
FEARS OF NUCLEAR CATASTROPHE
Guterres reiterated calls for demilitarisation around the nuclear plant.
"The facility must not be used as part of any military operation. Instead, agreement is urgently needed to re-establish Zaporizhzhia's purely civilian infrastructure and to ensure the safety of the area," Guterres said.
Russia, which captured Zaporizhzhia soon after its Feb. 24 invasion of Ukraine, said it could shut down the facility - a move Kyiv said would increase the risk of a nuclear catastrophe.
Moscow had earlier rejected as "unacceptable" international calls for a demilitarised zone around the nuclear plant, which is still operated by Ukrainian engineers under Russian occupation.
The power station sits on the Russian-controlled south bank of a huge reservoir; Ukrainian forces hold the north bank. Recent days have seen several incidents of shelling at the plant, which both sides blame on each other.
Ukraine also accuses Russia of using the plant as a shield for its forces to launch strikes across the reservoir on Ukrainian-held cities, which Moscow denies.
Reuters cannot independently confirm the military situation in the area or responsibility for shelling.
Zelenskiy said after meeting Guterres on Thursday that they had agreed parameters of a possible mission of the International Atomic Energy Agency to the plant.
"Russia should immediately and unconditionally withdraw its forces from the territory of Zaporizhzhia nuclear power plant, as well as stopping any provocations and shelling," he said.
Earlier, he accused Russia of "nuclear blackmail".
RECENT BLASTS AT RUSSIAN TARGETS IN CRIMEA
Moscow says its aim in Ukraine is to demilitarise the country and protect Russian-speakers on land that Russian President Vladimir Putin says historically belongs to Russia.
Kyiv and the West call it an unprovoked war to conquer Ukraine and erase its thousand-year national identity.
Russia has used Crimea, which it seized from Ukraine in 2014, to reinforce its troops fighting in other parts of Ukraine with military hardware, a process Kyiv is keen to disrupt ahead of a potential counter-offensive in southern Ukraine.
Ukraine has not officially claimed responsibility for a recent series of blasts in Crimea. Last week Moscow's Saki air base was devastated by a series of explosions that destroyed eight warplanes, according to satellite imagery.
Russia said this resulted from an accident, but Kyiv officials suggested it was part of a special operation.
Separately, blasts rocked an ammunition depot on Tuesday at a Russian military base in the north of the Crimean peninsula.
Russia blamed saboteurs, a rare admission that armed groups loyal to Ukraine are damaging military logistics and supply lines on territory it controls. Power lines, an electricity substation, railway infrastructure and some residential housing were also damaged.
Russian state media speculated that saboteurs may have used small drones to bomb the ammunition depot.
Ukrainian presidential adviser Mykhailo Podolyak said this week that Ukraine's strategy was to destroy Russian "logistics, supply lines and ammunition depots and other objects of military infrastructure. It's creating a chaos within their own forces."
(Reporting by Reuters bureaux; Writing by Peter Graff, Alex Richardson and Cynthia Osterman; Editing by Alison Williams, Gareth Jones and Daniel Wallis)