Turkish President Recep Tayyip Erdogan on Thursday accused Greek Prime Minister Kyriakos Mitsotakis of telling lies after Athens accused Ankara of "instrumentalising migration".
Ankara and Athens are often at loggerheads over migration, with the Nato allies accusing each other of failing to honour a deal to curb the flow of migrants passing through Turkey to Europe.
Mr Mitsotakis on Tuesday said Greece intercepted boats that came from Turkey, denying claims of pushing them back over the border.
"So rather than put the blame on Greece you should put it on those who have been instrumentalising migration systematically," he said.
Mr Erdogan, standing alongside visiting Hungarian Prime Minister Viktor Orban, accused Mr Mitsotakis of "acting dishonestly".
"It is Greece condemning refugees to their deaths in the Mediterranean and Aegean Seas," Mr Erdogan said. He said Turkey had "all the documents" to prove his claims.
"I have no idea how Greece would handle it if Turkey opened the doors" to migrants trying to reach Europe, as it briefly did during an escalation of the dispute last year, Mr Erdogan said.
Turkey signed a deal worth €6 billion ($6.87bn) with the EU in 2016 to stem the flow of migrants after more than a million people fled to Europe in 2015.
Turkey is home to about 3.6 million refugees from the conflict in Syria, and is often used as a transit country to Europe by migrants from countries including Afghanistan.