Gunmen firing on protesters in Cairo's Tahrir Square killed four people on Thursday as the thousands demanding President Hosni Mubarak go stood firm in their increasingly bloody 10-day revolt.
"All (four) were killed by gunshot, with one hit in the head," said Dr Mohammed Ismail, at a makeshift clinic in Abdulmenem Riad Square, next to Tahrir (Liberation) Square, taking the death toll over the past 24 hours to seven.
Dr Amr Bahaa, another medic treating people wounded in the clashes, had earlier reported receiving a wave of protesters hit by bullets, allegedly fired by plain-clothes police loyal to Mubarak's creaking regime.
"Most of the casualties came in in the last three hours, many with gunshot wounds," he told AFP early morning, putting the total wounded toll since Wednesday at more than 1,000 people.
The gunfire came after backers of Mubarak stormed the Cairo stronghold of anti-regime protesters Wednesday afternoon, sparking clashes in which the government said three people were killed.
The two sides fought battles with stones and Molotov cocktails through the night and into Thursday morning, with many of the square's paving slabs torn up and broken into fist-sized projectiles which now carpet the area.
Wounded 11-year-old Mohammed Ghozlan and his father Khaled were Thursday morning at a field clinic opposite the world-famous Egyptian museum, having spent the night on the square.
"Don't cry, don't cry, you're a hero," Khaled tells his son, who has a gash on the side of his head requiring four stitches.
"Every day we've been here, we're not going anywhere, I have five children, if they all have to die it's OK, we're not leaving until he leaves," he said referring to Mubarak, in power since 1981.
Doctor Mohammed Ismail, 34, has been treating the wounded in the capital of the world's most populous Arab nation since Tuesday.
"I want to say to Egyptians that our daughters and our sisters are here in this war and our men are sitting at home watching it on television. We are staying here until victory or death."
Protesters have erected corrugated iron and rubbish barricades on streets leading into the square, where thousands spent a chilly night, sleeping, chanting, throwing stones and nursing wounds.
Soldiers deployed around the square have retreated into their tanks and armoured personnel carriers, after a hail of rocks rained down on them for hours on Wednesday.
One in 10 people have some kind of visible injury, an AFP correspondent said, with volunteers distributing food and clothing to the exhausted protesters.
Citizens have built an improvised 10-foot (over two metre) high stone-throwing catapult out of planks and a crate
With the death toll rising, the US State Department issued a stark travel warning for citizens in Egypt, urging those who want to leave to "immediately" head for the airport, adding that any delay was "not advisable."
Washington, which has called for restraint since demonstrations broke out 10 days ago, deplored the violence against "peaceful protesters" while UN chief Ban Ki-moon said the attacks on demonstrators were "unacceptable."
America's top diplomat Hillary Clinton condemned the "shocking" bloody clashes Wednesday, in a call to Vice President Omar Suleiman.
The State Department said Clinton had called Suleiman, telling him the violence "was a shocking development after many days of consistently peaceful demonstrations."
"The secretary urged that the government of Egypt hold accountable those who were responsible for violent acts," the State Department added in a statement.
The European Union added its voice Wednesday to calls from US President Barack Obama for the transition from Mubarak's three-decade-long rule to begin immediately after the veteran president announced late on Tuesday that he would not seek re-election in September.
But the Egyptian foreign ministry said such calls "sought to inflame the internal situation," while Suleiman, who was appointed this week, insisted there could be no dialogue with the opposition until all the protesters went home.
From early Wednesday afternoon until well into the night, regime supporters and opponents threw stones and battled with sticks and fists in Tahrir Square, the epicentre of the 10 straight days of protests that have rocked the Egyptian regime and sent shock waves around the Arab world.
A hard core of tens of thousands of anti-regime protesters had remained at Tahrir Square through the night, angry at the 82-year-old's refusal to step down immediately in line with the demands of opposition leaders.
Both sides continued throwing rocks and skirmishing into the night, with army and civilian ambulances taking the wounded away.
Anti-regime protesters stopped handing over pro-Mubarak militants to the army as they said they were just being released. Instead, they kept some 30 of those they captured at an improvised prison in a metro station.
The captives were badly beaten, an AFP correspondent reported.
Several foreign journalists covering the confrontations in Cairo became the target of violent attacks, a media watchdog and news organizations said.
Correspondents, photographers and cameramen reporting on the fierce clashes in Tahrir Square said that the Mubarak supporters were hostile to the press.
Media watchdog group Reporters Without Borders (RSF) said the "shocking" attacks appeared to be in revenge for the coverage of the protests.
Protesters have said they will proceed with plans for a massive demonstration on Friday, their designated "departure day" for Mubarak.
US State Department spokesman Philip Crowley said the attacks on the protesters were a "direct threat" to the Egyptian people.