Exiled Belarusian opposition leader Svetlana Tikhanovskaya has urged the Polish government not to shut down border crossing points between the two countries.
"Keeping Belarusians connected to Europe is crucial," she said in a post on X, adding that people could not be left "behind a new iron curtain".
Earlier on Sunday, Poland's foreign minister said Warsaw was considering closing the remaining border checkpoints with Belarus to try to stem illegal migration.
Poland says that Belarus has been encouraging people from the Middle East and Africa to travel to Belarus and then cross the border illegally to Poland.
In 2021 the European Union accused Belarus's authoritarian leader Alexander Lukashenko of facilitating the influx in retaliation against sanctions.
In recent weeks Poland has closed four of the six checkpoints on the border with Belarus.
On Sunday Polish Foreign Minister Radoslaw Sikorski said: "Due to the actions of Belarus, we are considering the closure of all border crossings. For now, we are studying the question of whether this will affect the Polish economy."
In her post Ms Tikhanovskaya wrote: "Initiatives to limit border traffic due to the regime's ongoing provocations should target the dictator, not the people. We cannot abandon Belarusians to their fate behind a new iron curtain."
She was referencing the physical division of Europe during the Cold War between the Western countries and those connected to or influenced by the Soviet Union.
In 2020 Ms Tikhanovskaya went became a symbol of opposition when she ran against Mr Lukashenko in presidential elections after her husband was jailed by the regime.
She claimed victory in the polls, which were widely thought to be rigged, but was forced into exile in Lithuania with her children the day after the vote.
She was later sentenced in absentia to 15 years in jail for treason and conspiracy to seize power.