Witnesses said that gunshots rang out from a bridge leading to the square, the epicentre of protests against Mubarak for the past 10 days.

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An Al Jazeera correspondent, reporting from the scene, said it was not clear who was behind the firing.

There have been sporadic clashes throughout Thursday, as the army fanned out to separate the two sides and allowed thousands more protesters to enter their camp in the square.
Al Jazeera's online producer in Cairo said: "The battle for downtown Cairo on Thursday has taken on an almost medieval quality, with protesters erecting makeshift barricades and building homemade catapults to launch rocks at each other.

"Close-range combat ensued for several hours, with hand-to-hand combat near the barricades erected by pro-democracy protesters. Both sides threw hundreds of rocks back and forth."

Pro-democracy protesters gradually pushed back Mubarak loyalists who had swarmed onto a nearby highway overpass where they had been pelting their rivals with objects.

PM apologises

A day earlier, Tahrir Square had witnessed fierce clashes, after Mubarak loyalists - some of them riding camels and horses - attacked the pro-democracy protesters.

Ahmed Shafiq, the Egyptian prime minister, made an unprecedented apology on Thursday for Wednesday's assault that turned central Cairo into a battle zone.

"Egyptian hearts are bleeding," he said of the clashes in which at least five people were killed and hundreds hurt.

Shafiq said the attack on the anti-Mubarak protesters was a "blatant mistake" acknowledging that it was likely organised and promised to investigate who was behind it.

The pro-democracy protesters accuse the regime of organising the assault, using paid thugs and policemen in civilian clothes, in an attempt to crush their movement.

Egypt's state news agency has reported that the prosecutor-general has banned travel and frozen the bank accounts of three former ministers of the government that was sacked over the weekend, including the interior minister who was responsible for police.

The prosecutor-general said he ordered the same restrictions against a senior ruling party official until security is restored in the country.

Journalists targeted

On Thursday, mobile operator Vodafone complained about the use of the network by Egyptian authorities to send messages to the people of Egypt.

In a statement, Vodafone said: "These messages are not scripted by any of the mobile network operators and we do not have the ability to respond to the authorities on their content.

"Vodafone Group has protested to the authorities that the current situation regarding these messages is unacceptable.

"We have made clear that all messages should be transparent and clearly attributable to the originator."

Foreign photographers reported a string of attacks on them by Mubarak supporters on Thursday near Tahrir Square.

The Egyptian army rounded up several journalists after they came under attack from supporters of Mubarak.

"There is a concerted campaign to intimidate international journalists in Cairo and interfere with their reporting. We condemn such actions," PJ Crowley, the US state department spokesman, said in a statement issued via Twitter on Thursday.

The New York-based Committee to Protect Journalists said on Wednesday that violence against journalists was part of a series of deliberate attacks and called on the Egyptian military to provide protection for reporters.

Shahira Amin, a senior journalist at Nile Television, walked out on Wednesday in anger that state TV was not broadcasting enough of the protests and clashes in the square.