Large numbers of police and special counterterrorism officers sealed off a large square in the Polish capital on Saturday after a man climbed the top of a monument and threatened to blow himself up, the Polish news agency PAP reported.
The incident took place at Pilsudski Square, the site of a memorial to late President Lech Kaczynski and the dozens of other victims of a plane crash near Smolensk, Russia.
The man's intentions and whether he had an explosive device were not immediately known. Police said the officers were still on site and did not give any further details.
The incident came on the eve of a critical national election.
The country's de facto leader is Lech Kaczynski's surviving twin, Jaroslaw Kaczynski, while his ruling Law and Justice party is fighting for an unprecedented third straight term.
