A Romanian fighter jet on Sunday shot down a third drone that had entered its national air space in as many days, prompting President Nicușor Dan to blame Moscow for the "inadmissible and intolerable" incursions.

Sunday's incident marked the latest escalation for the NATO member. The series of incursions comes as Russian attacks on Ukraine's Danube region have increasingly spilled over the border.

"It is inadmissible and intolerable for the Russian Federation to continue violating Romania's airspace, which is, at the same time, NATO airspace and European Union airspace," Dan said on Sunday.