ATHENS, Greece (AP) — Greece’s government has condemned what it described as a provocative act by Turkey, whose fighter jets Athens says buzzed a helicopter carrying the Greek defense minister and the head of the armed forces who were visiting a Greek island.

Turkey, however, denied its jets had ever harassed the helicopter, saying they were simply on a routine flight.

Greek government spokesman Stelios Petsas said Monday the incident on Sunday was another indication that “Turkey often exceeds the limits of both the rules of international law and of course the rules of good neighborliness.”

NATO allies and neighbors Greece and Turkey have a long history of testy relations, and have come to the brink of war three times since the mid 1970s. They remain divided over a series of issues, including territorial claims in the Aegean Sea.

Tensions between the two increased recently, particularly after Turkish President Recep Tayyip Erdogan in late February declared his borders open to migrants wishing to leave to Europe. Although Turkey also shares a border with European Union member Bulgaria, it was only at its border with Greece that tens of thousands of migrants appeared, demanding to cross. Weeks of often violent clashes with border guards ensued.

In Sunday’s incident, Greek fighter jets repelled the two Turkish jets, Greek officials said. Local media reported that Turkish jets continued to fly over the Greek island of Oinousses during a visit there by Defense Minister Nikos Panagiotopoulos and the chief of the National Defense General Staff, Gen. Konstantinos Floros.

“Such behavior by Turkey doesn’t help in defusing tension, which both sides should be seeking at this time,” Panagiotopoulos said Sunday. The Greek Foreign Ministry described the incident as “another unacceptable Turkish action” which confirms “the negative role Turkey is playing in the region, insisting on anachronistic perceptions of international relations.”

Turkey, for its part, accused Greece of trying to escalate tensions.

“Our warplanes carried out the task of recognition within the framework of routine activities in the Aegean,” Turkish Foreign Ministry spokesman Hami Aksoy said in a written statement.

“Trying to escalate tensions by dramatizing routine flights is of no benefit to this country,” Aksoy said. “Instead, these issues should be addressed during the confidence-building process that was initiated by the two countries’ defense ministries.”

Suzan Fraser in Ankara, Turkey, contributed to this report.