Protesters against President Hosni Mubarak appeared to be gaining ground today as clashes and mayhem continued in downtown Cairo today.

The number of pro-government supporters dwindled over the morning but the two sides continue to throw rocks and firebombs at each others.

At one time the army moved between the two sides in its first attempt at intervention, but Mubarak opponents made forays from behind their barricades and eventually moved forward and the army retreated after firing shots into the air.

Four tanks, however, cleared a highway overpass from where Mubarak supporters had hurled rocks and firebombs onto the protesters.

Meanwhile the new Egyptian Prime Minister in a statement regretted yesterday's violence, which saw at least five people killed.

It was revealed that the new Vice President Omar Suleiman has met representatives of some opposition parties.

State media also announced that the Vice president would make 'an important announcement later today.

Mr Suleiman was also quoted saying that Mubarak's heir apparent, his son Gamal, would also not be a candidate in September's presidential elections.

The anti-government protesters accused Mubarak's regime of unleashing a force of paid thugs and plainclothes police to crush their unprecedented nine-day-old movement, a day after the 82-year-old president refused to step down.

They showed off police ID badges they said were wrested from their attackers. Some government workers said their employers ordered them into the streets.

The anti-Mubarak movement has vowed to intensify protests to force him out by tomorrow.

The notion that the state may have coordinated violence against protesters, who had kept a peaceful vigil in Tahrir Square for five days, prompted a sharp rebuke from Washington, which has considered Egypt its most important Arab ally for decades, and sends it 1.5 billion dollars (£1 billion) a year in aid.

"If any of the violence is instigated by the government, it should stop immediately," said White House Press Secretary Robert Gibbs.

Egypt's Interior Ministry denied sending plainclothes policemen to join the crowds attacking protesters.

State TV said Vice President Omar Suleiman called "on the youth to heed the armed forces' call and return home to restore order." From the other side, senior anti-Mubarak figure Mohamed ElBaradei demanded the military "intervene immediately and decisively to stop this massacre."

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