Egyptian President Hosni Mubarak ordered the resignation of his government ministers in the early hours of Saturday morning, promising to introduce new pro-democracy reforms. But the president refused angry calls shouted by large crowds across Egypt, to step down.

"I will not shy away from taking any decision that maintains the security of every Egyptian," Mubarak said.

It was Mubarak's first statement since anti-government protests began on Tuesday. Violence continued even as Mubarak made his address on state television.

News reports say at least 27 people, including three officers from the security forces, have been killed since protesters first took to the streets four days ago. Hundreds of people have been injured.

"I regret the innocent victims and casualties on both sides, citizens and police personnel," Mubarak said.

However, the president said that anti-government protests were part of a plot to destabilize Egypt and undermine his regime's legitimacy. He defended the crackdown by security forces.

Protests in several cities

For the first time since the unrest started, the military has been mobilized with tanks patroling the streets of Cairo. Egypt's army had watched from the sidelines for four days as the demonstrations tested the capabilities of the country's domestic law enforcement apparatus. There were unconfirmed reports of clashes between army forces and the police.

Anti-government protests continued on Friday in various cities across Egypt including Cairo, Suez and Alexandria. Demonstrators defied a nation-wide curfew and set fire to the ruling party's headquarters in Cairo on Friday and tried to storm the foreign ministry.

In Cairo, where riot police fired rubber bullets and tear gas to stop protesters advancing towards parliament, between 400 and 800 people were injured.

Obama calls for "concrete steps"

US President Barack Obama urged Mubarak to take "concrete" steps towards political reforms, saying he must turn "a moment of volatility" into "a moment of promise."

"I want to be very clear in calling upon the Egyptian authorities to refrain from any violence against peaceful protesters," Obama said, after aides said the White House was readying for any possible political scenarios in Egypt.

White House spokesman Robert Gibbs told reporters that the United States will review its more than $1 billion (735 million euros) in annual aid to Egypt in light of the demonstrations.

Other Western leaders have urged both sides to show restraint. Speaking at a press conference at the World Economic Forum in Davos, German Chancellor Angela Merkel urged the Egyptian leadership to allow peaceful protest.

"There is no point in locking up people or in reducing their access to information," Merkel said, alluding to the mobile phone and Internet restrictions implemented by the government in Cairo. "We must come to a peaceful dialogue in Egypt. The stability of the country is important but not at the cost of freedom of opinion."

In a statement, European Union chief diplomat Catherine Ashton also called on Egyptian authorities to "immediately and unconditionally release all peaceful demonstrators from detention."

ElBaradei under house arrest

Qatar-based Arab broadcaster Al-Jazeera reported earlier Friday that dissident opposition figure Mohamed ElBaradei had been detained at a mosque in Cairo following traditional Friday prayers and was subsequently placed under house arrest.

ElBaradei, who returned to Cairo on Thursday, spoke to the British newspaper The Guardian early on Friday before prayers, striking his hardest tone yet since flying into the country from Vienna.

"I'm sending a message to the world that Egypt is being isolated by a regime on its last legs," he told The Guardian.

"There is of course a risk to my safety today, but it's a risk worth taking when you see your country in such a state you have to take risks," he added. "I will be with the people today."

As the Mubarak regime cracked down on mobile phone and Internet services, effectively cutting the lines of communication between the opposition groups and restricting Egypt's contact with the rest of the world, ElBaradei called on the international community to take action.

"The international community must understand we are being denied every human right day by day," he said. "Egypt today is one big prison. If the international community does not speak out it will have a lot of implications. We are fighting for universal values here. If the west is not going to speak out now, then when?"

Author: Rob Mudge, Richard Connor (AFP, Reuters, dpa)

Editor: Mark Hallam