Pope Francis died on Monday at age 88, capping a 12-year pontificate characterized by his concern for the poor and message of inclusion, but also some criticism from conservatives who sometimes felt alienated by his progressive bent.

Thousands of people began filing through St. Peter’s Basilica to pay their final respects to Pope Francis on Wednesday at the start of three days of public viewing ahead of his funeral.

The funeral has been set for Saturday at 10 a.m. local time (4 a.m. ET) in St. Peter’s Square and will be attended by leaders, including U.S. President Donald Trump and Ukrainian President Volodymyr Zelenskyy.

Francis’ casket is available for public viewing in St. Peter’s Basilica. The basilica will be kept open until midnight on Wednesday and Thursday to allow the faithful to mourn. The public mourning period will end on Friday at 7 p.m. local time.

Francis’ death and funeral will usher in a carefully orchestrated period of transition in the 1.4 billion-strong Catholic Church, with cardinals gathering over the coming days before entering a conclave, the secretive ritual voting in the Sistine Chapel to elect a new pope.

There are 133 cardinals who are under 80 years old and eligible to vote, after two bowed out for health reasons, and the new pontiff will likely come from within their ranks. The conclave is not expected to begin before May 5.

Contributing: Associated Press