At least 10 migrants stranded along the European Union's eastern borders have died amid a week-long stand-off between Poland, Latvia and Lithuania on one side and Belarus on the other.
Belarus' autocratic leader Alexander Lukashenko has been accused of orchestrating the flow of migrants into his country so that they could be sent to its neighbours.
Mr Lukashenko has allegedly sought to punish Poland and Lithuania for harbouring dissidents and his opponents.
Critics say he is also seeking to pressure the EU into lifting sanctions imposed on the country over a disputed election last year that saw the strongman leader secure another term as president to extend his 27-year rule.
About 2,000 mainly Kurd migrants from the Middle East are massed along the Polish and Lithuanian borders, with no prospect of moving forward and Belarus also denying them the ability to return.
Poland's Prime Minister Mateusz Moawieki has accused Mr Lukashenko of waging "a war in which civilians and media messages are the ammunition".
He also compared the events to those that had cost Poland its statehood more than a century ago.
Why it matters
The unwitting pawns in this power game are the migrants, stuck in extreme cold conditions that led to a 14-year-old Kurdish boy from Iraq freezing to death on the Belarus side of the border.
Eight other people have died in the biting chill. Aid workers fear the real toll is higher, with more casualties to come as winter sets in.
There have also been warnings of a military confrontation.
Thousands of soldiers have been moved to the frontier by Poland and Lithuania. Polish soldiers in the border area of Bialowieza on Wednesday fired warning shots when several hundred migrants tried to storm their territory.
The spat has drawn in Turkey and the United Arab Emirates, which are accused of precipitating the crisis by flying migrants to Minsk. Turkey yesterday banned Syrians, Yemenis and Iraqis from flights to Belarus.
Russian President Vladimir Putin has sought to convince Europe to open lines of communication with Belarus, but the EU considers Mr Lukashenko's rule to be illegitimate and the proposal remains a non-starter.
Escalating tensions, Mr Lukashenko has announced that Russian nuclear bombers will patrol Belarus' western borders. He has also threatened to shut off the flow of vital gas from Russia to the EU, though that might trigger an angry reaction from Moscow.
With doctors, aid workers and journalists barred from entering frontier zones, the concern now is whether more migrants will die in what some have called a new and emerging kind of hybrid warfare.