Belarus' state-run airline said on Friday that it is banning Syrians, Iraqis, and Yemenis from incoming flights from Turkey at Ankara's request after Minsk was accused of bringing in migrants to send onto the European Union.
In a statement to citizens of the three countries posted on its website, Belavia said they would not be allowed on flights from Turkey to Belarus as of Friday "in accordance with the decision of competent authorities in Turkey".
Turkey's aviation authority has also said that it is to ban Iraqis, Syrians, and Yemenis from travelling to Belarus.
Nationals of Iraq, Syria, and Yemen are banned "from buying tickets and boarding for Belarus from Turkey's airports," Turkey's General Directorate of Aviation said on Friday.
In a message posted on its Twitter account, the Directorate said that this measure, due to "the problems of illegal crossing of the border between Belarus and the European Union", will remain in force "until further notice".
It follows reports that the EU has been trying to strike a deal with airlines to get them to prevent migrants from flying to the country.
Western members of the United Nations Security Council condemned Belarus for the "instrumentalisation of migrants" following an emergency session on the crisis on Thursday.
Thousands of migrants mainly from the Middle East have been trying to cross from Belarus into EU member Poland for months but tensions soared this week as coordinated efforts to cross were rebuffed by Polish border guards.
Western governments accuse Belarusian strongman Alexander Lukashenko of luring the migrants to his country and sending them to cross into EU member Poland in retaliation for sanctions.
Those sanctions came in response to a crackdown on the opposition in the wake of the 2020 presidential elections and Lukashenko's decision to ground a Ryanair flight earlier this year over Belarus to detain an activist.
The World Health Organization (WHO) said on Friday it is "very concerned" about the health situation for migrants at the border.
WHO European Director Hans Kluge said the migrants were "at the mercy of the weather as winter fast approaches".
"We call on all states to protect the right to health of refugees and migrants at the Belarusian border, many of whom are in need of medical assistance," the organisation added in a statement.
According to one of the WHO's technical missions at the Belarus-Lithuania border, 60% of the migrants needed "some form" of medical care.
A long-standing ally of Lukashenko, Russian President Vladimir Putin on Thursday told the European Union to start talking to Belarus if it wants to resolve the crisis.
Meanwhile, the defence ministries of both Belarus and Russia say they have conducted joint military exercises near the Polish border.
Minsk said that a "tactical" unit of paratroopers from both countries was involved in the activity in the Grodno region.
"After the landing, the Belarusian and Russian paratroopers will perform a number of combat training tasks," the ministry said on Telegram.