Police and protesters clashed in the capital and other parts of Egypt on Wednesday in a second day of rallies to demand the ouster of Hosni Mubarak, in the biggest protests of the president's 30-year rule.
The interior ministry had banned all further demonstrations and promised a crackdown after thousands turned out on Tuesday, and security officials said some 700 people had been arrested over two days.
The White House called for the ban to be lifted.
Police used water cannons and tear gas against demonstrators in a main central Cairo thoroughfare. And they fired rubber bullets as 500-600 people took to the streets in the port city of Suez to demand Mubarak's ouster.
Dozens were arrested in the Mediterranean port of Alexandria as they tried to reach a sea-front square to hold a second day of protests, witnesses said.
The one-sentence chant ringing out at every demonstration has summed up the demand from the street: "The people want the ouster of the regime."
The interior ministry had said further demonstrations were banned and anyone taking part would be prosecuted.
"No provocative moves, or protest gatherings, or marches or demonstrations will be allowed," the ministry said.
"Legal measures will be taken against anyone (in contravention), and they will be transferred to the prosecution," a statement continued.
But members of the pro-democracy youth group April 6 Movement, the driving force behind the protests, said they would take to the streets regardless.
"We've started and we won't stop," one told AFP on Wednesday.
"Everyone needs to head down to Tahrir Square to take over the square once again," the group said on its Facebook page which, along with people on Twitter, had helped to organise Tuesday's protests.
The group also urged Egyptians to carry on protesting.
"To continue what we started on January 25, we will take to the streets to demand the right to life, liberty, dignity and we call on everyone to take to the streets ... and to keep going until the demands of the Egyptian people have been met," it said.
Speaking about the protest ban, White House spokesman Robert Gibbs said it was important for the Egyptian government to demonstrate "responsiveness" to its people.
Asked whether the ban should be lifted, Gibbs said: "Again, yes. We're supportive of the universal rights of assembly and speech. Those are universal values."
For her part, US Secretary of State Hillary Clinton called on "all parties to exercise restraint and refrain from violence.
"We support the universal rights of the Egyptian people, including the rights to freedom of expression, association and assembly and we urge the Egyptian authorities not to prevent peaceful protests or stop communications including social media sites," Clinton said.
In Cairo, Prime Minister Ahmed Nazif said the "government is keen to guarantee freedom of expression through legitimate means," but he did not say what he meant by that.
Late on Tuesday, the interior ministry said security forces had decided to allow demonstrators "to voice their demands and exercise their freedom of expression," with a commitment to "securing and not confronting these gathering".
But it accused the Muslim Brotherhood of rioting and causing public disorder, which the group denied.
The protests, inspired by the uprising in Tunisia, are the largest in Egypt since bread riots in 1977, four years before Mubarak came to power.
So far three protesters and a policeman have died.
Among demands are the departure of the interior minister, whose security forces have been accused of heavy-handedness; an end to a decades-old state of emergency, which gives police wide powers of arrest and bans demonstrations; and a rise in minimum wages.
Egypt's stock market saw a sharp decline and the Egyptian pound hit a six-year low of 5.83 to the dollar on Wednesday.
French Foreign Minister Michele Alliot-Marie said in Paris on Wednesday that France regrets the loss of life in the anti-government protests and supports calls for more democracy "in all countries."
German Foreign Minister Guido Westerwelle said Berlin was "very worried" by unrest in Egypt and calld on all sides to refrain from violence.
