Moscow - The European Union and Belarus are locked in a stand-off over migrants that has come against a backdrop of tensions between the West and Minsk's backer Moscow.

Here is what you need to know about the crisis that has seen thousands of migrants trapped in dire conditions on the Belarus-Poland border.

- Crisis setting in -

Since the summer, thousands of migrants, mostly from the Middle East, have flocked to Belarus to try to enter Europe through neighbouring EU member states Poland, Latvia or Lithuania.

The West accuses Minsk of having lured the migrants with the promise of an easy crossing into the EU and then forcing them to stay at the border as retaliation for sanctions imposed over the regime's suppression of dissent in the ex-Soviet country.

Map showing the border crossing points between Belarus and Poland

Anxious not to repeat the migration crisis of 2015, the EU has backed Poland, Latvia and Lithuania, who have barricaded their borders despite the deaths of nearly a dozen migrants.

On Tuesday, Warsaw forces fired tear gas and water cannon in freezing temperatures on a crowd of hundreds of people who advanced on a border post after a week of living in a makeshift camp.

Polish Defence Minister Mariusz Blaszczak warned on Wednesday that the crisis could last "for months or even years".

Around 4,000 people are believed to be currently stranded along the Polish border, where the majority of the migrants are concentrated.

In a sign that the crisis is becoming entrenched, the Belarusian authorities put up some 1,000 migrants in a "logistical centre" this week -- a move that could make the camp a semi-permanent presence on the borders of the EU.

Polish forces fire water cannon in border clashes with migrants

- What the sides are saying -

The EU accuses Belarusian President Alexander Lukashenko of engineering the crisis to force the Europeans to restart dialogue, which the West cut off after his regime launched a crackdown on the opposition in the wake of a presidential election last year.

The strongman who has ruled Belarus with an iron fist for nearly three decades denies the claims.

This week he spoke twice by telephone with German Chancellor Angela Merkel in his first call with a Western leader since last year.

On Wednesday, his office said that direct talks between Belarus and the EU are imminent.

Poland will start building a wall along its border with Belarus

Germany, however, has not confirmed direct talks.

Berlin instead outlined a process of providing humanitarian aid and returning migrants involving the United Nations refugee agency UNHCR and the International Organization for Migration in cooperation with the European Commission.

Still, Merkel's spokesman Steffen Seibert said Wednesday that it is "useful" to speak with Minsk "to improve this humanitarian situation" even if the talks are with a leader whose legitimacy Europe and Germany do not recognise.

For Warsaw, the crisis is an opportunity to restore its image in the eyes of its partners, who accuse the Polish authorities of flouting principles such as the independence of the judiciary and the primacy of law.

Poland and the EU: a relationship under strain (Oct 2021)

By remaining steadfast and locking down its borders, Poland is serving as a rampart -- the first in the line of defence of Europe to prevent an influx of migrants.

Lukashenko's main political and financial backer Moscow, for its part, has cast itself as a mediator, welcoming on Wednesday direct contact between the EU and Minsk.

- Migrants are the big losers -

The migrants -- mostly Iraqi Kurds -- have abandoned everything in their countries, spending thousands of dollars to reach Belarus on a tourist visa, determined to reach Europe.

But the EU's borders appear to be impervious, with both the Baltic states and Poland determined to block their passage no matter the cost in terms of image.

Warsaw has deployed thousands of troops to the border and even plans to erect a wall.

As winter approaches, freezing conditions will only make life more difficult for the migrants, whose current choices are limited: stay in Belarus and hope Europe reconsiders, or return home.

Already between 200 and 300 Iraqis seem to have made their choice: a repatriation flight from Minsk is due to bring them back to Iraq on Thursday.

By Antoine Lambroschini