Egyptian army tanks and soldiers have moved to end violence between anti-government protesters and supporters of President Hosni Mubarak in Cairo's central square.
Troops had stood by for nearly a day as the two sides battled with rocks, sticks, bottles and firebombs.
But on Thursday, hours after automatic gunfire hit the anti-government protest camp at Tahrir Square, killing at least three protesters, soldiers carrying rifles could be seen lining up between the two sides.
Several hundred other soldiers were moving towards the front line. Four tanks cleared a highway overpass from where Mr Mubarak's supporters had hurled rocks and firebombs on to the protesters.
The pre-dawn firing escalated what appeared to be a well-orchestrated series of assaults on the demonstrators that began when Mr Mubarak supporters charged into the square on horses and camels on Wednesday, lashing people with whips, while others rained firebombs and rocks from rooftops. Anti-Mubarak demonstrators traded showers of rocks in a counter-assault which drove their attackers out of the square.
The protesters accused Mr Mubarak's regime of unleashing a force of paid thugs and plain-clothes police to crush their unprecedented nine-day-old movement, a day after the 82-year-old president refused to step down.
The anti-Mubarak movement has vowed to intensify protests to force him out by Friday.
He promised on Tuesday not to run for re-election in September, named a new government and appointed a vice-president for the first time.
And state TV has now reported that Mr Mubarak's son will not seek to succeed his father in elections later this year, the latest concession to anti-government protesters.
It was widely believed the president was grooming his son Gamal, 46, to succeed him despite significant public opposition.