ATHENS, Greece — Greek police said Tuesday they have arrested two terrorism suspects who had been planning attacks in the country aimed at causing mass casualties.

The suspects were allegedly part of an overseas terrorism network. They are being held at police headquarters in central Athens, authorities said.

Greece’s anti-terrorism police division and National Intelligence Service were involved in the arrest, according to a police statement, and were assisted by a foreign intelligence service that has not been named.

Police said the suspects had chosen a target of “high symbolism” and were making final preparations for the attack.

“Their aim was not only to cause the loss of life of innocent citizens, but also to undermine the sense of security in the country, while hurting public institutions and threatening (Greece’s) international relations,” the police statement said.