Thousands have queued in Warsaw to pay tribute to Lech Kaczynski and his wife
A row has broken out over the decision to bury Polish President Lech Kaczynski in Wawel cathedral in Krakow - a place reserved for Poland's kings and heroes.
Hundreds have taken to the streets of the southern city in protest at the plan for a second consecutive night.
Thousands have joined an internet campaign against it. Mr Kaczynski died in a plane crash on Saturday along with his wife and many senior officials.
A date for a presidential election will be set after the funeral on Sunday.
Acclaimed Polish film director Andrzej Wajda dubbed the burial arrangements "misplaced" and "hastily made as emotions ran high", in an open letter published by the newspaper, Gazeta Wyborcza.
"Lech Kaczynski was a modest and good man, but there is no reason for him to lie in the Wawel among the kings of Poland and Marshal Jozef Pilsudski [the founder of modern-day Poland]," he said.
Officials said the site in a crypt close to Marshal Pilsudski was chosen by church leaders and the Kaczynski family, which include Mr Kaczynski's twin, Jaroslaw - the leader of Poland's opposition.
But Mr Wajda said the decision "will spark protests and could cause the deepest splits in Polish society since 1989".
Hundreds of people staged a protest in front of the residence of Krakow's Archbishop, Stanislaw Dziwisz, on Tuesday evening, carrying banners reading: "Not Krakow, not Wawel", and "Are you sure he is the equal of kings?"
Late on Wednesday a second protest was held, as well as a smaller counter demonstration in favour of the plan.
A Facebook group called "No to the Kaczynskis' burial in Wawel" had attracted more than 26,000 members by Wednesday.
The site of the crash is still being pored over by investigators
Many world leaders are to attend Sunday's funeral, including US President Barack Obama along with the leaders of Russia, France and Germany.
Polish officials have said that elections for a new president will be held in June.
In a parliamentary document they wrote that there were "two possible dates" - 13 or 20 June.
Poland's acting President, Bronislaw Komorowski, is expected to name the exact date after consulting political parties.
The bodies of the presidential couple have been lying in state together at the presidential palace in Warsaw.
They were among 96 people on board the Polish government jet that crashed in heavy fog while trying to land in the Smolensk region of Russia.
They had been travelling to attend a memorial service for Polish military officers and others massacred by Stalin's secret police at Katyn in 1940.
Other victims of the crash, whose bodies are believed to have been badly disfigured or burnt in the crash, are being identified by forensic scientists in Moscow.
A number of the dead have yet to be retrieved from the wreckage, officials said.
Russian investigators believe pilot error was to blame for the crash.
Air traffic controllers who handled the plane have been quoted as saying the Polish crew refused three times to heed advice to divert to another airport because of poor visibility.