Turkish jet fighters were harassed by the Greek military over the Aegean when the neighboring country’s Patriot air defense system put the Turkish aircraft under radar lock, the military has announced.

Four F4-E/2020 Phantoms were put under radar lock by Greece’s Patriot missile defense system twice, for 15 seconds each time, at 3:20 p.m. Turkish time on Dec. 23, the military said in a statement on Wednesday. The jet fighters were on a training flight in international waters off Greece’s Ikaria Island in the Aegean, said the military.

Media reports quoted military sources as saying that this was the first time Turkish military aircraft were threatened by Greece’s long-range missile defense system. The military has also reportedly notified the Foreign Ministry about the incident.