The Egyptian government warned activists hoping to emulate Tunisian pro-democracy protesters that they face arrest if they go ahead on Tuesday with mass demonstrations some have billed as the "Day of Wrath".
The rallies have been promoted online by groups saying they speak for young Egyptians frustrated by the kind of poverty and oppression which triggered the overthrow of Tunisia's president. Similar calls have been made in other authoritarian Arab states.
Coinciding with a national holiday in honour of the police, a key force in keeping President Hosni Mubarak in power for 30 years, the outcome in Egypt on Tuesday is seen as a test of whether vibrant Web activism can translate into street action.
"The security apparatus will deal firmly and decisively with any attempt to break the law," the government's director for security in the capital Cairo said in a statement.
Since Egypt bans demonstrations without prior permission, and as opposition groups say they have been denied such permits, that means that any protesters may be detained.
Interior Minister Habib el-Adli has issued orders to "arrest any persons expressing their views illegally".
"I tell the public that this Facebook call comes from the youth," Adli said in an interview published by the state-owned newspaper al Ahram on Tuesday but released before midnight.
"Youth street action has no impact and security is capable of deterring any acts outside the law," he said, adding that he welcomed "stationary protests held for limited periods of time" and that police would protect the protesters.
"Our protest on the 25th is the beginning of the end," wrote organisers of a Facebook group with 87,000 followers. "It is the end of silence, acquiescence and submission to what is happening in our country. It will be the start of a new page in Egypt's history -- one of activism and demanding our rights."
Rights watchdog Amnesty International has urged Egypt's authorities "to allow peaceful protests".
But protests in Egypt, the biggest Arab state and a keystone Western ally in the Middle East, tend to be poorly attended and are often quashed swiftly by the police, who prevent marching.
The banned Muslim Brotherhood, seen as having Egypt's biggest grassroots opposition network, has not called on members to take part but said some would join in a personal capacity.
Cairo security director Ismail Shaa'er said the government had sent warnings to protest organisers that they would need an interior ministry permit: "In the absence of such permits, these demonstrations and sit-ins will be dealt with in a legal manner and those beyond the law will be arrested," he said.
Commenting on the wave of public unrest in Tunisia, Adli said talk that the "Tunisian model" could work in other Arab countries was "propaganda" and had been dismissed by politicians as "intellectual immaturity".
Activists and the opposition say the interior ministry refuses to issue protest permits, citing security reasons.
Sympathisers across the world have said they plan to protest in solidarity. In Kuwait, security forces detained three Egyptians on Monday for distributing flyers for the protests.
"On January 25th, Egyptian protesters will carry their cameras as their weapons," one Facebook user wrote, 10 days after Tunisians faced down their veteran leader's police state in a revolt flashed around the world in website images.
"They will use cameras to capture every policeman who will attack peaceful protesters and every scene of our protests to show it to the world."