Migrants were putting up tents at the Polish border after attempting to breach the barrier separating the two nations earlier on Monday, according to Belarusian sources. The group, estimated at between 3,000 and 4,000 people and reported to consist mostly of Iraqi Kurds, had approached the border from Belarus.

Poland accused Belarus of "fully" controlling migrant groups who were attempting to enter Polish territory. Warsaw said they were used for hybrid attacks against the EU country.

"By creating an artificial migration route and cynically exploiting migrants, [Belarus strongman Alexandar Lukashenko] is trying to destabilize Poland, Lithuania and Latvia, and to force the European Union to lift the sanctions imposed on the Minsk regime," the Polish government said.

What happened at the border?

Footage from the scene seemed to show Belarusian troops accompanying the migrants on the Belarusian side of the border. It was not immediately possible to verify the videos, however, as Polish authorities are keeping reporters out of the area due to a state of emergency, while journalists who are not aligned with the government have limited options to operate in Belarus.

Videos published by the Polish Defense Ministry also showed people attacking the razor wire with shovels and wire cutters as Polish troops sprayed gas canisters over the fence.

Independent Belarus agency reported that migrants managed to destroy the section of the border barrier, but that the Polish security forces managed to close the breach by forming a police line.

Polish Prime Minister Mateusz Morawiecki was holding an emergency meeting over the attempted incursion.

What has the international response been? 

German Interior Minister Horst Seehofer called on the EU to "stand together" during the crisis.

"We must help the Polish government secure their external border. This would actually be the task of the European Commission. I'm now appealing to them to take action," Seehofer told the Tuesday edition of the German Bild newspaper.

President of the European Commission Ursula von der Leyen called on the bloc's 27 member states to approve extended sanctions against "Belarusian authorities responsible for this hybrid attack."

"The Belarusian authorities must understand that pressuring the European Union in this way through a cynical instrumentalisation of migrants will not help them succeed in their purposes," she said in a statement. 

The use "of migrants for political purposes is unacceptable", von der Leyen said, adding that the EU would also look at how to sanction "third-country airlines" that bring migrants to Belarus. 

The United States condemned Belarus for "orchestrating" migrants flows to Europe.

"As long as the regime and Belarus refuses to respect its international obligations and commitments, undermines the peace and security of Europe and continues to repress and abuse people seeking nothing more than to live in freedom, we will continue to pressure Lukashenko and will not lessen our calls for accountability," US State Department spokesman Ned Price told reporters.

What is Belarus' stance?

Belarusian officials blamed the Polish side for escalating the clashes, saying that they used "tear gas against people asking for protection."

"In response … some of the refugees moved to more decisive action and started breaking down the Polish barrier," they told the country's state agency Belta.

Previously, the authorities in Belarus said they were taking "necessary measures to ensure the continuous functioning of international transport channels." Belarus officials also blamed Poland for the migrants' foray.

"This desperate move is due to the indifference and inhumane attitude of the Polish authorities," they said.

What do Polish officials say?

Poland accused the Belarusian government of planning a "major provocation" by getting migrants to cross the Polish border on Monday.

"Belarus wants to cause a major incident, preferably with shots fired and casualties," Deputy Foreign Minister Piotr Wawrzyk told Polish public radio.

His statement came after the Polish Defense Ministry published a video of the migrant group nearing the border town of Kuznica.

Stanislaw Zaryn, a spokesman for the ministry coordinating Poland's intelligence agencies, said the group is preparing to enter Poland "en masse."

He also claimed the migrants were "under a strict control of Belarusian armed units who decide which way the group can or can't go."

"It's yet another example of the [Belarus] regime's hostile activity targeted against Poland," he added.

Belarusian opposition news outlet NEXTA said most of the migrants were Iraqi Kurds, and that the group included many women and children.

DW correspondent Magdalena Gwozdz-Pallokat quoted a spokesperson for the border guard as having said: "If necessary, we will use all available means we can" to stop migrants entering the country.

She said that although public opinion largely supported the harsh measures used by the government so far in the crisis, she had met many people at the border who had also tried, unsuccessfully, to get supplies and warm clothing to the migrants in view of the cold weather.

What is the security like at the EU's borders with Belarus?

Poland has deployed additional border guards, police and the military at its Belarus border. According to the Defense Ministry, the country now has 12,000 soldiers in the region, up from 10,000 deployed ahead of the latest developments. Members of Poland's army reserve in the border regions were also put on full alert.

"We are prepared for any scenario," Polish Interior Minister Mariusz Kaminski said in a tweet on Monday morning.

Earlier on Monday, Polish authorities said they have averted "an attempt by migrants to forcibly cross into Poland" near Kuznica.

"The situation has been brought under control," they added.

Later, however, the Polish government warned that a "coordinated attempt" to enter its terittory "has just begun."

"Poland is taking adequate steps to defend its border, which is also the external border of NATO and the European Union. We are in constant contact with our partners — both in NATO and the EU."

Lithuania, another EU and NATO member bordering Belarus, also said it was moving soldiers to its border regions as migrants were gathering on the Belarusian side. Interior Minister Agne Bilotaite said Vilnius will consider declaring a state of emergency in the region on Monday.

Why are migrants heading from Belarus?

Warsaw has repeatedly accused Minsk of encouraging and coordinating illegal border crossings into EU member Poland in recent months.

Belarus strongman Alexander Lukashenko has been enraged by EU sanctions over his ferocious crackdown on anti-government protests. Brussels has accused Minsk of "weaponizing" migrants by flying them to the capital from abroad and taking them to the EU's doorstep.

Since July, large numbers of migrants from Iraq, Syria, Yemen and other troubled regions have been attempting to illegally enter the EU via Poland, Latvia and Lithuania.

At the same time, Poland has been facing accusations of pushing migrants back into Belarus instead of giving them a chance to ask for asylum.

dj,wd/rt (AP, Reuters, Interfax)