BUCHAREST, Romania (AP) -- Romania raised fighter jets early on Saturday for the second time this week after an unidentified object breached its airspace by the Black Sea, the Ministry of Defense said.

The small object was detected over the Black Sea moving toward Romania, a European Union and NATO member, at around 2:30 a.m, the ministry said in a statement.

Romania shares a 650-kilometer (400-mile) border with Ukraine and has previously complained over Russian drones entering its airspace as Moscow attacks Ukrainian targets along the Black Sea and Danube River. Fragments of Russian drones have also been repeatedly found on Romanian territory near the Ukrainian border.

Two F-18 jets of the Spanish Air Force and two F-16s of the Romanian Air Force were dispatched but did not spot the target, which disappeared from the radar, the ministry said.

Two Spanish F-18s and two Romanian F-16s also were dispatched on Thursday in a similar incident.