Demonstrators are on the streets of Cairo and other cities to call on embattled leader Hosni Mubarak to step down immediately.

The president of 30 years has said he will remain in control until September, when he will not stand for re-election.

Largely good-humoured demonstrators are streaming into Cairo's Tahrir (Freedom) Square, the scene of earlier clashes between pro and anti-Mubarak supporters.

There are fears there could be a repeat of the violence of recent days, which saw men throwing petrol bombs and rocks, and dishing out brutal beatings on the streets.

The country's defence minister Hussein Tantawi and other top officials from the army - which has promised not to fire on the protesters - have visited the square.

Thousands of protesters are also gathering in Alexandria, Egypt's second-largest city.

The US State Department is warning of a spike in violence today.

"We are bracing for a significant increase in the number of demonstrators on the streets and with that, given yesterday's events, the real prospects of a confrontation," said State Department spokesman PJ Crowley.

The New York Times reported that US officials are discussing plans for Mr Mubarak to step down immediately and hand power to a transitional government led by vice president Omar Suleiman and the army.

Mr Mubarak, 82, said yesterday he would have stepped down this week but feared chaos and the Islamist Muslim Brotherhood taking power.

In an interview with America's ABC News, he denied accusations that it was his hired thugs who had been stirring up the violence this week.

Mr Mubarak said he told Mr Obama: "You don't understand the Egyptian culture and what would happen if I step down now."

Peaceful demonstrations turned ugly this week with running battles between the rival camps.

Eight people have been killed and about 900 injured so far, according to official figures.

Sky News witnessed severe beatings being dished out to suspected plain-clothes policemen - who have been blamed for inciting violence - and pro-democracy protesters.

:: Video report on Egypt's feared secret police

Several foreign journalists have also been badly beaten by pro-Mubarak supporters.

Angry men carjacked an ABC News crew and threatened to behead the journalists, but the crew managed to talk its way free, the US network said.

Broadcaster Al Jazeera says its Cairo office has today been stormed by unknown men and the office has been "trashed".

The United Nations is evacuating hundreds of staff from Egypt, and US citizens desperate to leave have been told to assemble at Cairo airport by consular staff.

The crisis in Egypt is expected to dominate today's European Council summit in Brussels, where all 27 EU states are likely to put their names to a further statement calling for urgent reform.

Leaders will ask EU foreign affairs chief Catherine Ashton to examine how Europe can support a transition of power in Egypt, including preparations for free and fair elections.

Speaking as he arrived at the summit earlier, Prime Minister David Cameron called on Mr Mubarak to take firm steps towards "credible transition".

He said: "If we see on the streets of Cairo today state-sponsored violence, or the hiring of thugs to beat up protesters, then Egypt and its regime would lose any remaining credibility and support it has in the eyes of the watching world, including Britain."

Britain's Foreign Office has announced that a second charter plane will depart from Egypt on February 5 with Britons wishing to leave the country. The first flight arrived in the UK last night.

:: Anyone who wants to get a flight on the charter service can call 0207 0088 765 or 02 2791 6000 if dialling from within Egypt.

:: Returning Britons describe Egypt as a 'war zone'

© 2011 Sky News, all rights reserved.