Hosni Mubarak, Egypt's former president, is set to go on trial for corruption and unlawful killing before and during the revolution that ultimately led to his ousting.
Mubarak's appearance in a temporary court at the Police Academy in Cairo on Wednesday is to be screened live on Egyptian state television.
Hours before the trial, the former president was said to have landed in Cairo, Al Jazeera's Sherine Tadros reported.
"Reports are that a very short while ago, a plane carrying Hosni Mubarak did in fact land at the Police Academy complex," she said.
Earlier, state TV had reported that Mubarak's motorcade left the hospital in the Red Sea resort of Sharm el-Sheikh, where he was admitted in April.
"But all this has happened under a cloud of secrecy," Al Jazeera's Jamal El Shayyal reported from Sharm el-Sheikh.
"Journalists were not allowed to film anywhere near the hospital ... All we can take is the line given by the government and state media."
Speculation swirled until hours before the start of the trial about whether the 83-year-old would turn up to face charges.
Medical sources said members of his family had arrived at his hospital late on Tuesday, and an airport source said a medically equipped aircraft had landed at the local airport.
Protesters are determined to see him in the dock and are likely to be enraged if he does not appear. Mubarak will be the first Arab leader to face a trial following the uprisings.
Many Egyptians see the former president's illness as a ploy so ruling generals can avoid publicly humiliating the war veteran who ran the Arab world's most populous nation for 30 years until he was toppled on February 11.
Al Jazeera, along with a number of other media outlets, has been denied access to the trial by the Egyptian government.
Al Jazeera's Sherine Tadros reports from Cairo
Habib el-Adly, Mubarak's former interior minister, and six top police officers are also being charged with murder and attempted murder in connection with the 850 protesters killed during the uprising, according to the official charge sheet.
All eight could face the death penalty if convicted.
Separately, Mubarak and his two sons, Gamal and Alaa Mubarak, face charges of corruption.
The courtroom has been set up in what was once the Mubarak Police Academy, one of the multiple security, military and other civil buildings named after the president, though since his toppling his name has been dropped.
Hours before the trial, there were mild clashes outside the Police Academy between Mubarak critics and groups of his supporters, Al Jazeera's Tadros reported from the scene.
"There have been some scuffles," Tadros said. "Out of nowhere it seemed that dozens of people, probably over a hundred people [were] here throwing rocks at each other despite the very heavy security."
Riot police were then called in to separate the protesters, Tadros said.
Security is tight, with barbed wire and hundreds of troops around the compound. Efforts have been made to ensure spectators in the court are unable to get close enough to the defendants' cage to yell and throw objects at them, the interior ministry said.
About 600 people are expected to attend, including relatives of some of the protesters killed during the uprising.
Al Jazeera barred
Over 200 news outlets tried to gain accreditation to report from inside the trial, but only 10 foreign sources, not including Al Jazeera, were given access to cover the opening session.
Egyptian officials told Al Jazeera that the decision of which outlets to allow inside was based on geographical span, meaning where in the world the outlet's audience is.
When questioned about what source is covering Al Jazeera's audience, officials said that the Kuwait News Agency represents the same parts of the world.
"There's that flavour once again, that feeling, that the old tactics of controlling the message is at play," said Al Jazeera's Sherine Tadros, reporting from Cairo.