Gunfire aimed at anti-regime protesters killed four people in Tahrir Square early on Thursday, taking the death toll from clashes that have rocked central Cairo in the past 24 hours to seven, a medic said.
"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 Square.
Dr Amr Bahaa, another medic treating people wounded in the clashes, had earlier reported receiving a wave of protesters hit by bullets.
"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 on Wednesday at more than 1,000 people.
Witnesses said that there were many people wounded by fire coming from the October Bridge where partisans of embattled Egyptian President Hosni Mubarak were positioned.
Health minister Ahmed Hosni Farid had said that three people were killed and 639 wounded in bloody clashes on Wednesday between pro- and anti-Mubarak protesters in the centre of Cairo.
The fighting erupted when Mubarak loyalists stormed into Tahrir Square on Wednesday afternoon in what appeared to be an attempt to end protests calling on the president to quit.
Sporadic gunfire started around 4:00 am (0200 GMT) and lasted for about two hours, while some of the army tanks positioned around the square appeared to move from their positions but stayed in the area, an AFP correspondent reported.
Egyptian Jurists Alliance said in a statement that anti-Mubarak protesters in Tahrir Square were coming under fire and that several were killed or wounded.
"Everyone should move to rescue the youth of Egypt," the statement said.
"Fighting started at 4:00 am. Policemen dressed as civilians opened fire from the October Bridge," a witness told AFP at the Kasr El-Aini hospital where many ambulances were arriving.
Civilian cars also rushed casualties to hospitals. One sedan car was packed with wounded people, with one unconscious man carried on the engine hood.
Al-Arabiya television reported that army troops fired warning shots to fend off gunmen shooting from cars speeding along the October Bridge.
Gunfire targeted anti-government demonstrators in the Abdulmenem Riad Square, which is next to Tahrir Square, the television said.
After sunrise, anti-government protesters in Abdulmenem Riad Square and Mubarak supporters on the October Bridge were seen throwing rocks at each other.
An AFP photographer in Tahrir Square said thousands of opposition protesters spent the night in the square. Many stood around 5.30 am (0330 GMT) to perform the dawn prayer while others lit wood fires to warm themselves.
Protesters organised themselves in groups gathered at the barricaded entrances leading to the square in preparation for a feared storming attempt by Mubarak supporters.