Poland declared an emergency in two regions bordering Belarus on Thursday, following an increase in illegal migration that Warsaw has blamed on its neighbour and in the build-up to this week's Russia-Belarus "Zapad-2021" drills.
Parliament formally approved the emergency - the first order of its kind since Poland's communist days - on Monday, with 247 votes against repealing the president's decision, 168 for and 20 abstentions.
Prime Minister Mateusz Morawiecki called on all parties to back the measures, which ban mass gatherings and limit people's movements in a 3-km (2-mile) deep strip of land along the frontier for 30 days.
"We do not expect a decrease in tensions on the eastern border because in a few days the biggest military exercises in 40 years will start, 'Zapad-2021'," he told a news conference.
"...we are dealing with a wide-ranging political provocation. This political provocation concerns an attempt to illegally push thousands, tens of thousands of illegal migrants through Polish borders...," he told later the Parliament.
Poland and the European Union have accused Belarusian President Alexander Lukashenko of encouraging hundreds of migrants to cross into Polish territory to put pressure on the bloc over sanctions it has imposed on Minsk.
Belarusian Foreign Minister Vladimir Makei last week dismissed the accusations and blamed "Western politicians" for the situation on the border.
Poland has also said it could face "provocations" during the "Zapad", the Russian word for "West", military exercises. The main phase is due to start on Sept. 10.
"...it is not only a diplomatic conflict, it is an attempt to violate the integrity of the Polish state, the sovereignty of our borders, and we cannot and will not allow it," Morawiecki also told the Parliament.
Russia, which will join forces with Belarusian troops for the drills, says it is within its rights to exercise on its territory and has been clear about the numbers involved.
(Reporting by Alan Charlish and Pawel Florkiewicz; Additional reporting by Anna Koper; Editing by Kevin Liffey and Alex Richardson)