Hundreds of Iraqis have returned home on an Iraqi Airways flight from Belarus, where thousands of migrants have camped on the Polish border for weeks hoping to enter the European Union.

A total of 431 people were aboard the Boeing 747, according to a spokesman for the government of the autonomous region of Kurdistan, where many of the repatriated Iraqis came from.

Iraq's government organised the flight and said the repatriation was voluntary.

The flight landed in Erbil and later flew on to Baghdad but most of the passengers disembarked in the Iraqi Kurdish capital.

Several airlines have also said they are trying to stop would-be migrants from travelling to Belarus in the first place.

Meanwhile, Belarus has been clearing the camps where migrants had sheltered.

But officials have warned that the crisis may take time to defuse.

"We have to prepare for the fact that the situation on the Polish-Belarusian border will not be resolved quickly," Polish Defence Minister Mariusz Blaszczak said.

"We have to prepare for months or even years," he told Poland's Radio Jedynka.

Fabrice Leggeri, head of the EU border agency Frontex, also said the bloc should prepare for more "hybrid" migrant crises engineered for political ends.

"We have to prepare ourselves for situations like this which can arise quite quickly," he said, comparing the current standoff to one on the Greece-Turkey border last year.

Overnight, the Polish army said it had detained a group of about 100 migrants who had crossed the Belarus-Poland frontier, accusing Belarusian forces of leading the operation.

Thousands of migrants, mainly from the Middle East, are camped out or staying close to the border in dire conditions aiming to cross into the EU.

The EU says Belarus engineered the crisis in retaliation for sanctions on the ex-Soviet country.

Belarus and its main ally Russia have rejected the charges and have criticised the EU for not taking in the migrants seeking to cross over.

In the latest border incident, the Polish defence 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 metres away," it said.

Migrants aiming to cross the Belarusian-Polish border

"A group of about 100 migrants was detained," it said, adding that the incident happened near the village of Dubicze Cerkiewne.

"Belarusian special forces led yesterday's attack," it said.

Video footage released by the defence ministry appeared to show Polish soldiers surrounding a large group of migrants crouched down in a wooded area at night next to some barbed wire.

EU-Belarus hold 'technical talks'

Belarusian President Alexander Lukashenko, who has ruled with an iron fist for nearly three decades, has spoken to German Chancellor Angela Merkel on the crisis twice in recent days.

Mr Lukashenko's press service said that he and Mrs Merkel "agreed that the problem as a whole will be brought up to the level of Belarus and the EU.

"Relevant officials, to be determined from both sides, will immediately start negotiations to resolve the existing problems," it said.

Mrs Merkel's spokesman Steffen Seibert said the German leader had "underlined the need to provide humanitarian care and return options for the affected people".

An EU spokesman said there were "technical talks" and urged Minsk to grant humanitarian access to the border area.

Aid groups say at least 11 migrants have died since the crisis began in the summer.

They have called for a de-escalation and a humanitarian response to the problem.

A child in Bruzgi on the Belarusian-Polish border where migrants have been offered temporary accommodation

Poland estimates there are 3,000-4,000 migrants along the entire border, with the largest group staying close to the shut down Bruzgi-Kuznica border crossing.

The Belarusian Red Cross says around 1,000 migrants are staying in a warehouse near that crossing and 800 more are camped nearby.

Ukraine stops 15 people from Middle East at Belarus border

Ukrainian border guards have stopped a group of 15 people from the Middle East, believed to be posing as tourists, from crossing the border with Belarus, a statement said, the first such intervention by Ukraine since the escalation of the migrant crisis.

Kiev has sent additional forces to reinforce its borders.

"Currently, the servicemen of the State Border Guard Service have decided not to allow entry and to return the travellers to the Republic of Belarus, as these persons had no grounds to enter the territory of our state," the statement said.

The group, which included four teenagers, had travelled to the Ukrainian border from the Belarusian capital Minsk, and said they wanted to go sightseeing in the western Lviv region before returning home, the statement added.

But the border guards grew suspicious because the group all had passports issued in the same period in September and October.

Also, the group had arrived weeks ago in Minsk and immediately headed to the western Grodno region of Belarus that borders Poland, the statement said.

Ukraine has accused Russia of helping Belarus to stir up the crisis, which Moscow denies.

Ukraine's parliament has passed legislation authorising border guards to use military equipment, firearms and physical force.