Thousands are out in the streets for a successive day after security forces using water cannons and tear gas cleared under the cover of darkness, large crowds gathered at a prominent city landmark in the early hours on Wednesday.

The government had banned all protests on Wednesday, a day after thousands of Egyptians across the country poured into the streets, clamouring for an end to the 30-year old dictatorship of President Hosni Mubarak.

Four people have been killed in clashes, including a police officer. Egyptian medical sources said around 150 protesters were injured, most of whom have been hospitalised. Police fired around 50 teargas canisters, which covered Tahrir square, the focal point of the agitation, with stinging grey smoke.

On Tuesday, protests were held all over Egypt, including the coastal city of Alexandria, already under stress on account of the recent attacks on its Christian community, Suez and North Sinai.

Despite the clampdown, protests simmered in Cairo and other locations on Wednesday. The Egyptian daily Al Masry Al Youm reported on its website that protesting journalists managed to release a prominent scribe who had been picked up by the police during the course of a demonstration on Wednesday.

Thousands gathered outside a Lawyers syndicate shouting slogans “bread, freedom and social equality.” In North Sinai, villagers protested for a second successive day, seeking the release of several young men who have been taken into custody, especially in the notorious Wadi al-Natroun prison. Reuters reported that hundreds of demonstrators had gathered outside the mortuary in Suez calling for the release of one of the three bodies.

It was clear that protesters have several political demands which go beyond seeking an end to the high food prices. Posted first on Facebook, these demands were circulated handwritten on plain slips of paper among the crowds that had assembled at Tahrir square on Tuesday, Al Jazeera reported. The crowds called for the resignations of President Mubarak, Prime Minister Ahmed Nazif, dissolution of parliament and the formation of a new national unity government.

"Down with Hosni Mubarak, down with the tyrant”. “We don't want you," the crowds chanted.

The Muslim Brotherhood, an organisation which did not formally participate but allowed its members to join the protest posted on its website, Facebook’s role in coordinating the marches. It said that the Facebook group for Khaled Said, an Alexandria resident, who was beaten to death by police last year, was one the main organiser of the protest. Around 80,000 people had pledged to join the protests online.

On Wednesday, Egyptian authorities blocked Facebook, following up on a similar move on Tuesday against the micro-blogging site Twitter. Meanwhile, the Arab Network for Human Rights Information (ANHRI), a human rights advocacy group, on Wednesday has demanded the sacking of Egypt’s interior minister Habib Al Adly, following Tuesday’s violent incidents. Observers say that his security apparatus has been accused of thousand s of human rights violations after Mr. Adly was appointed interior minster in 1997, with a mandate to destroy Islamist militant organisations.