A Russian fighter intercepted a Polish plane patrolling for the EU's border agency over the Black Sea, Romania's defence ministry said Saturday, denouncing Moscow's "aggressive and dangerous" behaviour.

The Polish border guard plane was on a routine Frontex patrol with Romanian border police Friday when it was intercepted by repeated "aggressive and dangerous maneuvers", performed by the Sukhoi Su-35 fighter, said a ministry statement.

Romanian and Spanish planes were put on "pre-alert" by NATO when the incident happened, but the Polish crew managed to land safely, the statement added.

The incident took place "in international airspace over the Black Sea," around 60 kilometres 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.

Contacted by AFP, the European border agency Frontex did not immediately respond. Polish border guards declined to comment, saying a statement would be issued on Sunday.

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.