Romanian prosecutors announced on Friday they had ordered the arrest of a man suspected of spying for Moscow, while the government declared a Russian diplomat persona non grata on its territory.

The arrest of the spying suspect marks the first of its kind in Romania since the start of Russia's war on Ukraine more than two years ago.

Prosecutors said the arrested man, a Romanian citizen, had "since 2022, been monitoring Romanian or NATO military objectives located near the municipality of Tulcea", a town near the border with Ukraine.

He is suspected of "collecting military information and taking photographs of military combat equipment and the movement of personnel in the border area with Ukraine, which he transmitted to diplomats from the Russian embassy in Bucharest," prosecutors added.

Romania's foreign ministry said subsequently that a diplomat from the Russian embassy had been declared "persona non grata on the territory of Romania" for activities in breach of the Vienna Convention on diplomatic relations.

The ministry said it had summoned the Russian charge d'affaires to notify the latter of the decision.

Authorities did not disclose the spying suspect's age or identity.

Romanian media quoted unnamed sources as saying the man was standing as an independent candidate for the post of mayor in the city of Ploiesti.

His name does not however appear on any official list of candidates for the local elections on June 9.

Since Russia's invasion of Ukraine in February 2022, several cases of alleged spying for Moscow have come to light in European countries, notably the UK, Germany and Poland.