Egyptian activists who spearheaded the revolt that toppledpresident Hosni Mubarak have called for mass demonstrations on Tuesday to protest against verdicts handed down in the strongman's murder trial.

Mubarak Mubarak and his interior minister Habib al-Adly were sentenced to life in prison on Saturday but six security commanders were acquitted over the killings of demonstrators during last year's uprising that left around 850 people dead.

The ruling sparked outrage across the country, with protesters who took to the streets furious that no one had been found directly guilty of killing the protesters.

The lack of police accountability under Mubarak was one of the main driving forces behind the uprising, and both activists and rights groups fear the acquittals will help sustain that culture of impunity.

The pro-democracy April 6 movement, the Coalition of Revolution Youth and the Maspero Youth Union among others called for a mass protest at the iconic Tahrir Square at 1500 GMT on Tuesday.

The runners-up of last month's presidential election, leftist politician Hamdeen Sabbahi and moderate Islamist Abdel Moneim Abul Fotouh will lead separate marches to the square in centralCairo, they said in statements.

The two came third and fourth respectively in the May 23-24 election that has narrowed to a presidential runoff later this month between Mubarak-era minister Ahmed Shafiq and the Muslim Brotherhood's Mohammed Mursi.

Pro-democracy movements have capitalised on the national anger, calling for a return to Tahrir to press for the goals of the revolution.

On Sunday, Egypt's state prosecutor said he would lodge an appeal against the sentences, but a judicial source told AFP the process could take weeks.

Mubarak's defence team has also said it would challenge the ruling and told AFP it was confident of winning on appeal.

Five of the six security chiefs were freed early on Monday, but the head of the now-dissolved state security apparatus, Hassan Abdel Rahman, remains in prison pending investigation into another case in which he is accused of destroying state security documents.

Mubarak -- the only autocrat toppled in the Arab Spring to be put in the dock -- could have been sent to the gallows as demanded by the prosecution but was handed down life term, angering some protesters.

He was also cleared of graft charges.

Along with acquitted police chiefs, Mubarak's sons Alaa and Gamal had corruption charges against them dropped on a technicality, prompting protests in Cairo, Alexandria and other cities.

On Sunday, the ex-dictator was issued regulation blue prison uniform and guards at the Cairo Tora prison took his official mugshot and gave him his prisoner number, state news agency MENA reported.

A tearful Mubarak, who enjoyed near absolute power for three decades, was flown by helicopter to the prison on Cairo's outskirts after the verdict but then refused to leave the aircraft.

The verdicts have triggered nationwide outrage and international criticism.

Mubarak's sentence "is a significant step towards combatting long-standing impunity in Egypt" but the security chiefs' acquittal "leaves many still waiting for full justice," Amnesty International said.

The verdicts come just two weeks before a presidential election run-off that will pit Shafiq against the Brotherhood's Mursi in a highly polarised race.

The runoff has left many activists faced with a difficult choice.

For them to choose a Mubarak-era figure would be to admit the revolution was over and to vote for Mursi would mean to hand the country to a movement they say has monopolised power since the uprising.

With less than two weeks to go before the runoff, the boycott movement has picked up pace, endorsed by celebrities such as actors Khaled el-Sawy and Amr Waked.