A few hundred people with banners and gold-and-silver hypothermia blankets march in Warsaw, Poland, on Saturday, Nov. 20, 2021, in support of the migrants stranded at the Belarus-Poland border. AP
Later Sunday the Polish head of government will meet his counterparts from the Baltic states -- two of which also share a border with Belarus -- to discuss the conflict, before visiting other EU capitals this week.
Belarusian President Alexander "Lukashenko launched a hybrid war against the EU. This is (the) greatest attempt to destabilise Europe in 30 years," Morawiecki said on Twitter.
"Poland will not yield to blackmail and will do everything to defend the EU's borders."
The West accuses Belarus of artificially creating the crisis by bringing in would-be migrants -- mostly from the Middle East -- and taking them to the border with promises of an easy crossing into the European Union.
Belarus has denied the claim, instead criticising the EU for not taking in the migrants.
Belarusian President Alexander Lukashenko told the BBC on Friday that it was "absolutely possible" his forces had helped people cross into the EU but denied orchestrating the operation.
"We're Slavs. We have hearts. Our troops know the migrants are going to Germany... Maybe someone helped them," he said.
"But I didn't invite them here."
Though there are signs the crisis is easing a little, on Sunday Poland's border guards reported new attempted crossings, including by a "very aggressive group of around 100" migrants.
Poland's Defence Minister Mariusz Blaszczak said Saturday that Belarus has now changed tactics by directing smaller groups of migrants to multiple points along the border.
The migrants have abandoned everything in their countries, spending thousands of dollars to fly into Belarus on tourist visas, determined to reach the European Union.
Polish media say at least 11 migrants have died since the crisis began over the summer.