President Recep Tayyip Erdogan has ordered the Turkish coastguard to prevent migrants from crossing the Aegean Sea because of the risks, state media reported.
"On the orders of the president ... permission will not be given for migrants to cross the Aegean Sea because it is dangerous," the coastguard was quoted as saying by Anadolu news agency late Friday.
On Saturday tensions flared on the Greek-Turkey border, where thousands of migrants amassed at a makeshift camp waiting to cross into Europe.
The Associated Press reported at least two migrants were injured in the latest clash between Greek police and migrants gathered on the Turkish side of a crossing near the Greek village of Kastanies. Officers in Greece fired tear gas to impede the crowd, and Turkish police fired tear gas back at their Greek counterparts, the AP reported.
Greek soldiers and riot police have been manning the borderland, and Greek officials say authorities have thwarted thousands of attempts by migrants to cross in the past eight days. Over a 24-hour period by Saturday morning, there were more than 1,200 attempts to cross and 27 arrests, a government source said.
"Greece is doing what every sovereign state has the right to do, to protect its border from any illegal crossings," Greek Prime Minister Kyriakos Mitsotakis told the CNN network on Friday night.
"I'm afraid this is a constant and very systematic provocation on Turkey's behalf which has nothing to do with the plight of these people. They are being used by Turkey."
Erdogan's communications director Fahrettin Altun said Turkey "categorically" rejected Mitsotakis' claims.
Heavy machinery was moved to the border crossing area on the Greek side on Saturday morning and a bulldozer was seen digging embankments close to Kastanies, a border town.
On the Turkish side of the border, Turkish police have banned journalists from accessing the makeshift migrant camp at Pazarkule, but some migrants are managing to sneak out and tell their stories, reports FRANCE 24.
Turkey said on February 28 that it would let migrants cross its borders into Europe, saying it could no longer contain the tens of thousands who have been trying to cross since that date, nor a potential fresh influx of migrants due to intensified fighting in northwest Syria.
Turkey on Friday accused the European Union of using migrants as political tools after EU foreign ministers said they would work to stop illegal migration into the bloc.
The EU on Friday pleaded with migrants on the Turkish border to stop trying to cross into Greece but dangled the prospect of more aid for Ankara as a standoff entered a second week.
Most of the migrants were from Afghanistan and Pakistan.
(FRANCE 24 with AFP, AP and REUTERS)