Pro-Russian separatist authorities in the Moldovan breakaway region of Transnistria on Sunday said that an explosion at a military site had likely been caused by a drone launched from Ukraine.

Transnistria is a primarily Russian-speaking region that has long depended on Moscow for support, and broke away from Moldova after the collapse of the Soviet Union.

"Today a fire occurred on the territory of a military base in Tiraspol as a result of an explosion," authorities said on social media.

"It was preliminarily established that the explosion was caused by a kamikaze drone attack," they added, claiming the drone was launched from the Odesa region of Ukraine.

Separatist officials said no one was hurt and opened a criminal investigation.

There was no immediate comment on the incident from Kyiv or in Moscow.

Grainy footage distributed by separatist authorities showed a projectile slamming into a military helicopter standing at an airbase surrounded by fields.

Late last month, Transnistria appealed to Russia for "protection," fuelling fears the territory could become a new flashpoint in Moscow's conflict with neighbouring Ukraine.

In 2006 the separatist territory's deputies announced a referendum on integrating with Russia that resulted in an overwhelming majority in favour.