Most of the several hundred thousand protesters who thronged the square Tuesday had gone home, but the hardcore that have occupied the now iconic space for 12 days remained in place in makeshift shelters.

As the sun came up over the huge area, ringed by imposing administrative blocks, upscale hotels and a cordon of government troops backed by a squadron of tanks, small groups began to chant their defiance of the regime.

Essam Magdi, a 35-year-old lawyer, has been sleeping under the tracks of a tank since January 28 to prevent it from moving off.

"They want to push us deeper into the square. They want to move us, so we sleep here. We love the soldiers and we trust them, but we don't trust their commanders," he explained.

Mubarak's deputy, Vice President Omar Suleiman, has attempted to take the heat out of the protest by beginning a dialogue with selected opposition groups to reform the constitution and prepare free elections.

But in Tahrir, the protesters' key demand remains that Mubarak must go.

"There can be no negotiation until he leaves. After he leaves we can talk about all sorts of things," said Magdi, as a nearby loudspeaker blared: "Don't be tired. Don't be tired. Freedom isn't free."

The presence of the banned Muslim Brotherhood at the protests has caused some in Western capitals to fear the movement might be hijacked by Islamists.

But the demonstrators -- Islamists, secularists, leftists, liberals and frustrated non-ideological youths mobilised by internet cyberactivism -- all insist their goal is free elections open to all.

"We didn't want a military state or a religious state. We want a state of institutions and elections," said 34-year-old Atif Awad, a carpenter and a member of the Muslim Brotherhood.

Ahmed Mabruk, 32, who qualified as an engineer but works as builder, said the movement has no leaders yet, but is an expression of Egyptian popular will. "Everything you see here is from the people," he said.

The demonstrators plan to hold the square until Mubarak falls, and have been joined daily by supporters bringing food and staging street rallies. Tuesday's were the biggest yet, packing the area in defiance of a nightly curfew.