The Polish army detained dozens of migrants who crossed the Belarus border and accused Belarusian special forces of masterminding the operation, as G7 foreign ministers on Thursday urged Minsk to end the migrant crisis.
Around 2,000 people, mainly from the Middle East, are estimated to be living near the Poland-Belarus border in dire conditions and desperate to cross into the European Union.
The EU says Belarus engineered the crisis in retaliation for sanctions on the ex-Soviet country. Minsk and its main ally Russia have rejected the charges and criticized the EU for not taking in the migrants seeking to cross over.
"We call on the regime to cease immediately its aggressive and exploitative campaign," the EU and foreign ministers of the G7 global powers said.
But Belarus has said it wants to de-escalate the crisis.
Belarusian President Alexander Lukashenko's spokeswoman Natalya Eismont said on Thursday that there were currently around 7,000 migrants in the country.
She said Belarus will send 5,000 of the migrants home, while German Chancellor Angela Merkel will negotiate with the EU on creating "a humanitarian corridor to Germany" for the 2,000 on the border.
There was no immediate reaction from Germany.
A repatriation flight with between 200 and 300 migrants on board took off from Belarus on Thursday bound for Erbil in Iraqi Kurdistan and Baghdad.
The flight traveling to Baghdad is carrying 431 people, Russia's Interfax news agency reported.
200 migrants detained
In the latest border incident, the Polish defense ministry said that Belarusian forces had first carried out reconnaissance and "most likely" damaged the barbed wire fence along the border.
"Then the Belarusians forced the migrants to throw stones at Polish soldiers to distract them. The attempt to cross the border took place several hundred meters away," it said.
"Belarusian special forces led yesterday's attack," it said.
The border guard said a total of around 500 migrants took part in the attempted crossing and 200 of them were detained after crossing into Poland successfully.
It said a family of five people, including three children aged between seven and nine, had been injured in the incident and were taken to hospital.
Video footage released by the defense ministry appeared to show Polish soldiers surrounding a large group of migrants crouched down in a wooded area at night next to barbed wire.
The incident could not be independently verified as journalists are banned from the immediate border area on the Polish side.
EU-Belarus 'technical talks'
Lukashenko, who has cracked down on political opponents and independent media for nearly three decades, has spoken twice to Merkel about the crisis in recent days.
Lukashenko's press service on Wednesday said the Belarus leader and Merkel "agreed that the problem as a whole will be brought up to the level of Belarus and the EU."
The Polish government has warned against any agreement on the crisis that might be struck "over our heads."
Poland's state-run TVP network also on Thursday began broadcasting a new English-language channel TVP World, bringing forward the launch to "show the whole world the truth" about the migrant crisis on the Poland-Belarus border.
Meanwhile British Defense Secretary Ben Wallace said he would stand "shoulder to shoulder" with Poland during a visit to a military base in northeast Poland that hosts a NATO battlegroup.
A squadron of British military engineers is expected in Poland later this month to help with border fencing and repairing roads in the area, Polish Defense Minister Mariusz Blaszczak said.
Child's death reported
Aid groups say at least 11 migrants have died since the crisis began in the summer.
Polish medical workers said they had assisted a Syrian couple in the early hours of Thursday who had been in the forest for one and a half months.
"Their one-year-old child died in the forest," the Polish Center for International Aid said on Twitter.
In another incident, video footage released by Belarusian border guards showed a Lithuanian border guard dog biting a man lying on the ground in a sleeping bag.
Lithuania's boder guard admitted to the incident, saying that they were attempting to push back a group of migrants into Belarus and that the border guard did not see the migrant.
Charities have called for a de-escalation and a more humanitarian response to the problem.