Monday marks the 87th month since a Polish plane crashed in Smolensk, western Russia, killing all 96 on board, including the Polish president and first lady.
The event is commemorated monthly in Warsaw with a Catholic Mass and a procession to the Presidential Palace.
But anti-government protesters have in the past brushed with mourners, largely supporters of the conservative Law and Justice (PiS) government.
“I truly ask all those who have sentiments of democracy and freedom on their lips not to take away the freedom [of assembly] of others,” Deputy Interior Minister Jarosław Zieliński said.
Zieliński said that police offer protection for all legal public gatherings.
After coming to power in October 2015, PiS – headed by the twin brother of the late president who died in the Smolensk disaster – passed laws giving priority to regular, recurring public gatherings.
The new laws, which came into force in April, forbid counter-protests at the same place and time.
PiS has long challenged an official report into the crash issued by the previous Polish government which cited a catalogue of errors on the Polish side, while also pointing to errors made by Russian staff at the control tower of Smolensk Military Airport.
A Russian report placed all the blame on the Poles.
PiS has launched its own inquiry into the crash which, in initial findings, suggested the plane was probably destroyed by a mid-air explosion, and that Russian air traffic controllers deliberately misled Polish pilots about their location as the presidential plane approached the runway of the Smolensk military airport in 2010.
During monthly commemorations known as the "March of Remembrance", marchers gather for a Mass before proceeding through the streets of Warsaw to the Presidential Palace, where PiS leader Jarosław Kaczyński, brother of Lech Kaczyński, the president who died in the Smolensk crash, addresses the crowd.
In June several dozen anti-government protesters sat down on Warsaw's Krakowskie Przedmieście street in an attempt to block the march's route. Some were forcibly moved by police.
Former Polish President and Nobel Peace Prize winner Lech Wałęsa was to attend an anti-government counter-gathering on Monday in protest against the new laws on public assemblies, but he is in hospital with circulation problems and may not be able to go.
Wałęsa was the leader of the Solidarity movement which conducted dozens of strikes and held protests which helped bring down the communist regime in Poland in 1989. (vb/pk)
Source: PAP