LONDON — Britain, France, Germany and the US have stressed the need to ensure the safety of nuclear installations threatened by the conflict in Ukraine.

In a phone call on Sunday, the four leaders also reiterated their support for Ukraine against Russia's invasion.

Moscow and Kyiv have accused each other of shelling a Russian-held nuclear plant, raising fears of a catastrophe.

Meanwhile, President Volodymyr Zelensky urged Ukrainians to be vigilant ahead of Independence Day celebrations.

"Russia could try to do something particularly disgusting, particularly cruel," he said in a weekend address.

"One of the key objectives of the enemy is to humiliate us," he added, but "we have to be strong enough to resist all provocation".

Ukraine's Independence Day on Wednesday, 24 August, will also mark six months since Russia invaded Ukraine.

The conflict was the subject of a conference call on Sunday bringing together the UK's Boris Johnson, US President Joe Biden, his French counterpart Emmanuel Macron and German Chancellor Olaf Scholz.

Following its conclusion, they urged military restraint around the Russian-controlled Zaporizhzhia nuclear power station in southern Ukraine, where renewed fighting has led to fears of disaster worse than that in Chernobyl in 1986.

The leaders welcomed a deal - approved by Russian President Vladimir Putin on Friday - to allow UN inspectors to visit the plant at a future date.

The four leaders also said they had "agreed that support for Ukraine in its defense against Russian aggression would be sustained".

Ukraine reported more missile strikes on Sunday, notably in the town of Nikopol, near the Zaporizhzhia power station.

On Saturday, a fresh drone attack targeted Russia's Black Sea fleet in the city of Sevastopol in Russian-annexed Crimea. The Russian authorities there said a Ukrainian drone had been shot down.

Several drone strikes have been reported in Crimea in recent days, including one on an airbase near Sevastopol on Thursday and another on the harbor on Friday.

Earlier in the month, nine Russian jets were destroyed at a Russian military base on Crimea's western coast.

The peninsula was invaded and annexed by Russia in 2014 and Ukraine has vowed to retake it. However, Kyiv has not confirmed or denied involvement in the recent attacks.

In Russia itself, the daughter of a close ally of President Putin, the ultra-nationalist philosopher Alexander Dugin, was killed in a suspected car bombing late on Saturday.

Darya Dugina, 29, died after an explosion on a road outside Moscow.

It is thought her father, who is known as "Putin's brain", may have been the intended target of the attack.

Both had been guests at a patriotic festival. Aleksandr Dugin's writing about the need to restore the Russian empire is believed to have inspired President Putin. — BBC

Daughter of Putin ally killed in Moscow blast

Putin, Moscow blast, car bomb, Darya, Dugina, Dugin, Alexander, Putin’s brain, Zakharovo

MOSCOW — The daughter of a close ally of Russia's President Vladimir Putin has been killed in a suspected car bombing.

Darya Dugina, 29, died after an explosion on a road outside Moscow, Russia's investigative committee said.

It is thought her father, the Russian philosopher Alexander Dugin, who is known as "Putin's brain", may have been the intended target of the attack.

Dugin is a prominent ultra-nationalist ideologue who is believed to be close to the Russian president.

Alexander Dugin and his daughter had been at a festival near Moscow, where the philosopher gave a lecture on Saturday evening.

The "Tradition" festival describes itself as a family event for art lovers which takes place at the Zakharovo estate, where Russian poet Alexander Pushkin once stayed.

The pair were due to leave the venue in the same car, before Dugin reportedly made a decision at the last minute to travel separately.

Footage posted on Telegram appears to show Dugin watching in shock as emergency services arrive at the scene of the burning wreck of a vehicle.

Investigators confirmed that Ms Dugina, who was driving the car, died at the scene near the village of Bolshiye Vyazemy.

They said an explosive device planted under the car went off and the vehicle caught fire. Forensic and explosive experts are investigating.

A Ukrainian official has dismissed accusations of Ukrainian involvement in the incident.

"Ukraine, of course, has nothing to do with this, because we are not a criminal state, which is the Russian Federation, and even less a terrorist state," said Mykhailo Podolyak, an adviser to President Volodymyr Zelensky.

Maria Zakharova, spokeswoman for Russia's foreign ministry, said in a Telegram post that if any Ukrainian link was found it would amount to "state terrorism".

Despite not holding an official position in government, Alexander Dugin is believed to be a close ally of the Russian president and has even been branded "Putin's Rasputin".

Darya Dugina was herself a prominent journalist who vocally supported the invasion of Ukraine.

Earlier this year she was sanctioned by US and UK authorities, who accused her of contributing to online "disinformation" about Russia's invasion.

In May, she described the war as a "clash of civilizations" in an interview and expressed pride in the fact that both she and her father had been targeted by Western sanctions.

Alexander Dugin was sanctioned by the US in 2015 for his alleged involvement in Russia's annexation of Crimea.

His writings are said to have had a deep influence on Putin and the philosopher is regarded as a chief architect of the ultra-nationalist ideology endorsed by many in the Kremlin.

For years, Dugin has called on Moscow to assert itself more aggressively on the global stage and has supported Russian military action in Ukraine. — BBC