Violence erupted in the Egyptian capital as security forces clashed with people protesting a decision to throw out charges against former President Hosni Mubarak over the killing of protesters during a 2011 uprising.

Egyptian security forces shot one person late on Saturday, either with live ammunition or birdshot, as they moved in and cleared the protesters off the streets.

Dozens more demonstrators, some hurling rocks, were injured as tear gas and birdshot were fired near Cairo's iconic Tahrir Square.

Around 2,000 people had gathered to protest the decision to dismiss murder charges against Mubarak, his interior minister and six aides over the deaths of nearly 900 demonstrators in the 18-day uprising that toppled the former leader.

Mubarak and his sons, Alaa and Gamal, were also cleared by Chief Judge Mahmoud Kamel al-Rashidi of corruption charges related to gas exports to Israel.

The judge said too much time had elapsed since the alleged crimes took place for the court to rule on the matter.

Reacting to the verdict, Mubarak denied responsibility for the protesters' deaths, in a phone call to a local television station.

"I felt I did nothing wrong at all. I was waiting to find out what they will come up with this time. It was an innocent verdict. I did nothing wrong at all," he said.

"But, we cannot change destiny. When I heard the previous ruling I laughed. This time I was just waiting. I felt indifferent. It is all in the hands of God."

Mubarak, 86, did not walk free after Saturday's verdicts. He was found guilty in May in another case, related to the theft of public funds, and he has been serving that three-year sentence, under house arrest for medical reasons, in an army hospital in a posh Cairo suburb.

'An oppressive ruling'

Saturday's rulings can be appealed and the attorney general has asked his team to study the case to see if that is possible.

Those cleared of charges include: Hosni Mubarak , former president

, former president Alaa and Gamal , sons of Hosni Mubarak

, sons of Hosni Mubarak Habib Aladly , former interior minister

, former interior minister Ahmed Ramzi , former head of central security forces

, former head of central security forces Adli Fayed , former assistant for interior minister

, former assistant for interior minister Hasan Abd Elrahman , former head of state security

, former head of state security Ismael Alshaer , former head of security in Cairo

, former head of security in Cairo Osama Almarasi , former head of security in Giza

, former head of security in Giza Amr Alfaramawi , former head of security in 6 of Oct area

Mubarak, wearing sunglasses and a sweater, had been grim-faced when he was wheeled into the courtroom on a stretcher.

The judge said the former president should not be on trial in the first place.

"It is not suitable for a former president to be taken to a criminal court, according to the terms and conditions of criminal law, or to consider the things he did wrong within his political responsibilities, even those crimes mentioned in the accusation list," he said.

Mubarak's supporters leapt out of their benches in celebration when the judge pronounced the verdict, chanting: "Say the truth, don't be scared, Mubarak is innocent."

Outside the court venue, a sprawling police academy on Cairo's outskirts, relatives of those killed in the uprising were appalled at the ruling.

"It's an oppressive ruling. The blood of my son has been wasted," Mostafa Morsi, whose son was killed outside a police station during the uprising, told the AFP news agency.

Though nearly 900 protesters were killed, the trial was concerned only with the killing of 239 protesters, whose names were cited in the charge sheet.

While delivering his judgement, Rashidi praised the uprising, saying that its goals - freedom, bread and social justice - were justified.

The overthrow of Mubarak, who ruled for about 30 years, led to Egypt's first free election but the winner, Mohamed Morsi, was toppled last year by the army.

The release of some Mubarak-era figures this year had already raised fears among activists that the old leadership was regaining influence.