Turkey threatened Greece on Wednesday to stay out of its activities in the eastern Mediterranean, suggesting a potential showdown with Athens and Nicosia over hydrocarbons research in the region.

Turkish Defence Minister Hulusi Akar said Ankara would not tolerate “further Greek harassment of Turkish vessels” after reporting last week that a Greek warship hassled a Turkish exploration ship west of Cyprus.

Greece has denied the allegations.

Tensions have heightened already this week, after Turkey warned Greece on Tuesday it would not accept an expansion of Greek territorial sea boundaries, a few days after Athens said it planned to extend its territorial waters from 6 miles to 12 miles.

“Our warships are providing the necessary protection in the region. We will never tolerate new harassment,” said Akar.