Russian-installed officials also shut a stretch of the motorway that crosses the southern half of the peninsula.

They did not explain the cause of the fire at a military training ground near the city of Staryi Krim.

But unconfirmed reports on social media spoke of three Ukrainian strikes.

The overnight explosions coincided with a heavy Russian missile and drone attack that officials said was largely targeted at Ukraine's southern city of Odesa.

Critical infrastructure and military facilities were attacked by several waves of cruise missiles and Iranian-made drones launched from the Black Sea, Crimea and southern Russia, said Ukraine's air force.

Although 37 Russian missiles and drones were shot down, a number did penetrate Ukrainian defences. Officials in Odesa said a number of people were wounded and several flats were damaged. A grain and fuel terminal at the port were hit along with two warehouses including one described as housing fireworks.

"I saw a red flash in the window and reacted immediately," one resident told the Reuters news agency.

"The moment I fell on the floor behind the bed, all the windows were blown out.

"I went downstairs, it was noisy and filled with smoke outside, people were in panic, some were crying, glass shards were scattered all over. It was impossible to remain the area."

It was the second night in a row that Odesa was targeted, in attacks linked to Russia's withdrawal from an international deal enabling grain and fertiliser to be exported safely across the Black Sea.

"Every Russian missile is a blow not only to Ukraine, but to everyone in the world who wants a normal and safe life," he said on social media.