Some 20,000 police officers and soldiers will guard the upcoming trial of Egypt’s toppled president, an official said Thursday, as Islamist opponents plan massive protests that may spark more turmoil in the country.

An Interior Ministry official warned that any protesters attempting to break into the courtroom where ousted President Mohammed Morsi will be tried will be met “decisively with force.”

The stark warning came as a Muslim Brotherhood-led coalition called Thursday for mass demonstrations across the country today until Nov. 4, set as opening day of Morsi’s trial.

Morsi, a Brotherhood leader, faces charges of inciting murder and violence in connection to deadly clashes at the presidential palace in December. He’s been held at an undisclosed location since the military toppled him in a popularly supported July 3 coup.

It is not yet clear if the 62-year-old Morsi will appear in court, though the Interior Ministry official said that the ousted president will be flown by helicopter to the Tora prison complex. The trial will be held inside a police institute near the prison in southern Cairo, where most of the group’s arrested leaders are held, the official said.

It has not been announced yet whether Morsi will return to the undisclosed location or join other detained Brotherhood members in Tora prison after the hearing. Another security official said authorities favor holding him away from Tora to avoid the prison becoming a focal point for protesters, though civilian authorities likely will take responsibility for him from the start of the hearing.

The officials spoke on condition of anonymity as they weren’t authorized to speak publicly about security arrangements for Morsi’s trial.

Some fear the trial will mark a new cycle of turmoil in Egypt. In a statement, the Brotherhood-led coalition described the trial as “illusionary” and said it would hold authorities responsible for any harm that comes to Morsi.

“We have seen in the era of the coup those committing the crime are the ones who are presenting President Mohammed Morsi to be tried,” the statement read.

Morsi’s trial is part of efforts by the military-backed interim government to break the Brotherhood. Nearly 2,000 Brotherhood members have been arrested since the coup, while top leaders face criminal charges. Meanwhile, authorities are pushing to quickly amend the country’s constitution and hold parliamentary and presidential elections by early next year to cement their legitimacy.

Egyptians already have seen former President Hosni Mubarak — overthrown in popular uprising in 2011 — on trial.

The security crackdown on the Brotherhood saw security forces violently clear protest camps in Cairo, leaving hundreds dead and sparking weeks of unrest.

Many fear that the violence will start again as Morsi goes on trial, especially with the heavy security cordon planned and the possibility of protesters clashing with police. Security forces arrested 20 women after clashes Thursday in the Mediterranean city of Alexandria, authorities said.

The Interior Ministry official said that security forces will be deployed on the streets around the prison starting Saturday, two days before the trial. He said they will close all entrances to trial site, while “combat teams” will be on rooftops surrounding Tora prison “to abort any plots by the Muslim Brotherhood to foil the trial.”

During Egypt’s 18-day uprising in 2011, protesters accused police of shooting at them from rooftops.

“Any attempt to smuggle prisoners, storm the courtroom or get near Tora prisons … will be dealt with decisively, with force and by law,” he said.