According to Poland's border force, the Russian Sukhoi Su-35 plane did not make radio contact before carrying out "aggressive and dangerous manoeuvres, approaching the border guard plane three times without keeping to the required safety distance".

The Polish plane, an L-410 Turbolet, experienced turbulence and the crew temporarily "lost control of the aircraft and lost altitude", the border force said.

It added the Russian plane flew just in front of the nose of the aircraft and crossed its path at a distance of "around five metres" (16 feet).

Government spokesman Piotr Muller told Polish television it was a "planned provocation by Russia".

Late Saturday, Romania's defence ministry, which first reported the move, condemned Moscow's "aggressive and dangerous" behaviour.

Romania said the Polish plane was on a routine Frontex patrol with Romanian border police Friday when it was intercepted.

The Polish aircraft landed safely in Romania afterwards.

Romanian and Spanish planes were put on "pre-alert" by NATO, the Romanian statement added.

It took place "in international airspace over the Black Sea," around 60 kilometres (37 miles) east of Romania's airspace, said the ministry.

"This incident is further evidence of the provocative approach of the Russian Federation in the Black Sea," said Bucharest.

The European border agency Frontex did not immediately respond when contacted by AFP.

The Polish plane has been deployed in Romania from April 19 and is due to stay there until May 17, part of a Frontex operation organised by Romania that also includes Spain and Sweden.