WARSAW, Poland — Turkey on Friday halted airline ticket sales to Iraqi, Syrian and Yemeni citizens wanting to travel to Belarus, which in recent months has become a key launching point for migrants and refugees trying to enter the European Union illegally.

The move, announced by Turkey’s Civil Aviation Authority, follows EU pressure on airlines to stop bringing people from the Middle East to Minsk, the capital of Belarus.

Starting from there, thousands of asylum-seekers have managed to slip into EU member nations Poland, Lithuania and Latvia since the summer, though many others have also been kept from entering or pushed back.

The crisis involving a large number of migrants stuck at the EU’s border threatens to become a humanitarian crisis as winter approaches. It is also creating another point of tension between the West and Belarus’ authoritarian regime.

On Friday, Russia sent paratroopers to the Grodno region in Belarus, which borders Poland, in a show of support for its ally. That follows Russia’s sending nuclear-capable strategic bombers to patrol over Belarus for two straight days this week.

Among the migrants are Iraqi Kurds and Syrians fleeing conflict, persecution or poverty. Many aim to reach Germany or other western European countries, sometimes to reunite with relatives already settled there.

In a brief statement posted on Twitter, Turkey’s aviation authority said its decision to halt ticket sales was valid until further notice.

Citing the Turkish decision, Belarusian airline Belavia said it would not transport citizens of Iraq, Syria and Yemen on its Istanbul-Minsk flights starting Friday. Belavia said in a statement that it planned to reimburse the cost of already purchased tickets.

The EU said it also received confirmation that Iraqi Airways, which halted flights to Minsk in the summer, will not resume them.

EU and Polish officials have accused the longtime leader of Belarus, President Alexander Lukashenko, of facilitating illegal border crossings in retaliation for sanctions the EU imposed on his government for its brutal crackdown on dissent following Lukashenko’s disputed reelection last year.

German federal police reported this week that 1,246 unauthorized entries to Germany “with a connection to Belarus” had been recorded in the first nine days of November. In all, there have been 9,087 such entries so far this year, German police said.

Polish authorities said a large number of people remain just across the border in neighboring Belarus, and that Polish border guards, police and soldiers continue to rebuff attempts to enter each day.

Hundreds of people, including families with children, are in makeshift camps on the Belarusian side of the border. Attempts to cross have become increasingly dangerous as Poland fortifies its side of the border and pushes people back and as temperatures drop to below freezing at night.

The World Health Organization said it sent an expert team to Lithuania to assess migrants held in reception facilities there and found that 60% were in need of some form of medical treatment.

The organization’s Europe regional director, Dr. Hans Kluge, said he was “very concerned about the thousands of vulnerable people who are stranded in no-man’s land on Belarus’ borders with Poland, Latvia and Lithuania, at the mercy of the weather as winter fast approaches.”

“Women and children are sleeping outdoors in the bitter cold. Several people have already died. And COVID-19 cases are rising sharply across the region,” he said, stressing that people’s rights to health and shelter are protected by international law.

A Polish official said the country’s ongoing conflict with Belarus’ government is not expected to ease in coming days. Paweł Soloch, head of the National Security Bureau, said Poland faces a “a psychological, hybrid war, waged consciously by centers that want to weaken or even ultimately destroy our country.”

Nevertheless, Poland’s Border Guards said that on Thursday they recorded 223 attempts to illegally cross from Belarus, fewer than earlier in the week.

To date Poland has not asked Frontex, the EU border agency, to help, but has requested assistance returning migrants to their home countries.

Frontex chief Fabrice Leggeri told EU lawmakers Thursday that there are 1,700 Iraqis to be returned from Poland to Iraq, with an initial group of 200 ready to travel. He said he has asked the EU Commission to help persuade Iraq to accept chartered flights, because it’s easier to return 200 people on two flights than 6 or 7 Iraqis every day on commercial flights.

Leggeri also said that reports of gunshots fired from the Belarusian side of the border mean it would “not be a safe place to deploy an operation.”

Poland’s Defense Ministry said one group of migrants ran along a Polish border fence but was were stopped by officials. It posted what it said was a video of the incident.

The Border Guards agency posted another video on Twitter which it said shows Belarusian personnel using a green laser at the border.

“We assume that these were attempts to blind our officers and soldiers patrolling the border,” the post said.

The information was impossible to verify. Independent journalists face limits to their reporting in Belarus, and a state of emergency in Poland’s border zone prevents media from entering the area.