Nobel peace laureate and Egyptian opposition politician Mohamed ElBaradei has arrived in Cairo as anti-government protests continue to spread.
A Bedouin protester was shot dead in the Sinai region on Thursday, bringing this week's death toll to seven.
There were also protests in the cities of Cairo, Suez and Ismailiya.
The governing party says it is willing to listen to public grievances such as unemployment but has cracked down on protests, arresting up to 1,000 people.
Speaking on his arrival in Cairo, Mr ElBaradei said he would join the protests
"I wish we did not have to go out on the streets to press the regime to act," he said, according to Reuters news agency.
The protests are expected to increase on Friday, when the weekend begins in Egypt and millions gather at mosques for prayers.
As he left Vienna, where he now lives, Mr ElBaradei told reporters: "If [people] want me to lead the transition, I will not let them down."
'No other option'
Mr ElBaradei, formerly the head of the UN nuclear watchdog, the IAEA, said the government should not use violence against the demonstrators.
"I continue to call on the regime to understand that they better listen and listen quickly, not use violence and understand that change has to come. There's no other option," Mr ElBaradei added.
Meanwhile, the governing National Democratic Party (NDP) of President Hosni Mubarak says it is open to dialogue. But it has warned protesters to remain peaceful, ahead of major demonstrations expected on Friday.
"They are free to express their demands and we are here to meet their needs," said NDP secretary general Safwat al-Sherif.
"I hope that all preachers at Friday prayers tomorrow are calling people to be peaceful in a clear, ritual way that never plays upon people's feelings to achieve an undesirable target."
US President Barack Obama described the protests as the result of "pent-up frustrations", saying he had frequently pressed Mr Mubarak to enact reforms.
"The government has to be careful about not resorting to violence," he said in a YouTube question-and-answer session. "The people on the streets have to be careful about not resorting to violence."
The US counts Egypt as a key ally in the Middle East.
Police and demonstrators have again clashed in Cairo and Suez, and the unrest has now spread to the industrial city of Ismailiya.
Thursday's protests in Cairo have been on a much smaller scale than the thousands seen on Tuesday and Wednesday. However, in Suez, police fired rubber-coated bullets, tear gas and water cannon, witnesses said.
In Suez, a fire station was set alight by demonstrators.
In Ismailiya, hundreds of protesters fought with police, who used batons and tear gas to disperse them.
The Egyptian stock exchange suspended trading temporarily after a sharp drop within minutes of opening, but its benchmark index has fallen further since re-opening.
The protest organisers have urged people to come out in force again after attending prayers in mosques and churches on Friday, stressing that the religion of protesters is not relevant.
The Muslim Brotherhood has given its backing to the planned protests. Despite an official ban, it remains Egypt's largest and most organised opposition movement.
Egyptian President Hosni Mubarak, 82, has not been seen in public since the protests began on Tuesday.
The Egyptian government tolerates little dissent and opposition demonstrations are routinely outlawed.