Egypt's government warned of a military crackdown as massive rallies against President Hosni Mubarak spread and reports surfaced that the army had detained and tortured pro-democracy activists.
Hundreds of demonstrators marched on parliament from the epicentre of the uprising in Cairo's Tahrir Square on Wednesday, a day after the largest protests since the revolt began, as unrest spread across the nation.
Foreign Minister Ahmed Abul Gheit warned the army, until now a mostly neutral force, would intervene if the protests against Mubarak's 30-year-old US-backed rule escalated.
"If chaos occurs, the armed forces will intervene to control the country, a step... which would lead to a very dangerous situation," the official MENA news agency said, paraphrasing Abul Gheit's interview with Arabic-language satellite television channel Al-Arabiya.
His remarks came after newly appointed Vice President Omar Suleiman warned of a possible "coup" in the absence of a peaceful transfer of power.
Abul Gheit slammed the United States for "imposing" its will on Egypt by demanding immediate reforms.
"When you speak about prompt, immediate, now, as if you are imposing on a great country like Egypt, a great friend that has always maintained the best of relationship with the United States, you are imposing your will on him," he said.
Shortly after his comments, Washington renewed its calls on the Egyptian army to show restraint.
The protesters however showed no sign of backing down on their demand for Mubarak to go as tens of thousands of people filled Cairo's Tahrir Square well into the third week of a revolt.
Around a thousand marched on parliament to demand its members' resignation, vowing to remain until the legislature -- widely seen as unfairly dominated by the ruling party -- is dissolved.
Meanwhile, rights groups and demonstrators told Britain's Guardian newspaper that the army had secretly detained hundreds of anti-government protesters, some of whom were tortured.
"Their range is very wide, from people who were at the protests or detained for breaking curfew to those who talked back at an army officer or were handed over to the army for looking suspicious or for looking like foreigners," Hossam Bahgat, director of the Egyptian Initiative for Personal Rights in Cairo, said.
"It's unusual and to the best of our knowledge it's also unprecedented for the army to be doing this," he added.
One man said he was detained in the Museum of Egyptian Antiquities after being apprehended by the army while taking medical supplies to protesters injured by Mubarak's supporters.
"They put me in a room... then soldiers started kicking me. They got a bayonet and threatened to rape me with it.
"They said I could die there or I could disappear into prison and no one would ever know," he added.
In Tahrir Square, volunteers built portable toilets, indicating the protesters have no intention of leaving the "liberated" area, now a sprawling tent city with sound stages, flag vendors and a mobile phone charging station.
On Wednesday, unrest gripped the remote oasis of Kharga, where at least five people were killed and 100 wounded when security forces opened fire on demonstrators, a security official told AFP.
In the Suez Canal city of Port Said, some 3,000 protesters stormed a government building, torching office furniture and the governor's car. There were other protests across the country.
The 82-year-old Mubarak has charged Suleiman, his longtime intelligence chief, with drawing selected opposition groups into negotiations on democratic reform before elections due in September.
Some parties have joined the talks, but the crowds in Tahrir Square insist that Mubarak must go before they will halt the protest.
The Muslim Brotherhood, the country's best organised opposition group despite a half century of illegality, meanwhile moved to reassure observers who fear an Islamist takeover should Mubarak's regime be toppled.
"The Muslim Brotherhood does not seek power. We do not want to participate at the moment," senior leader Mohammed Mursi told reporters, adding that the movement would not field a presidential candidate.
The United States is watching events in the most populous Arab country with great concern, hoping the transition to elected rule can take place without a descent into violence, or an Islamist or military takeover.
White House spokesman Robert Gibbs said the government had yet to meet the "minimum threshold" of reform demanded by Egyptians.