ISTANBUL ­— Greek armed forces were placed on high alert Tuesday after a Turkish ship began seismic surveying activities near the Greek island of Kastellorizo that will continue until Aug. 2.

The Turkish navy announced the development through a NAVTEX advisory Tuesday, setting off a potentially dangerous escalation between the two nations that have for years held overlapping territorial claims in the eastern Mediterranean Sea.

The Greek Foreign Ministry issued a statement Tuesday, calling on Ankara to “immediately cease the illegal activities” that it said violated the nation’s sovereign rights. On Wednesday, the Turkish Foreign Ministry rejected the assertions, saying the Oruc Reis survey ship was operating within Turkey’s continental shelf.

“Greece bases this claim on the presence of remote islands far from its own mainland, most notably Kastellorizo,” Turkish Foreign Ministry Spokesperson Hami Aksoy said in a statement Wednesday. “This maximalist continental shelf claim of Greece is contrary to international law, jurisprudence and court decisions.”