More than 10,000 protesters opposing Egyptian President Mohammed Morsi swarmed the square in front of his Cairo palace on Friday evening, breaking through barbed wire barriers protecting the compound.
A cordon of soldiers prevented the crowd from nearing the main palace gate in the Egyptian capital, but elsewhere protesters sprayed graffiti on the outside walls, telling Morsi to "Go" and leave power.
"The people want the downfall of the regime" and "Leave, leave," they chanted, using slogans from the uprising that toppled Morsi's predecessor Hosni Mubarak in February 2011.
Climbing over tanks of the Republican Guard, protesters streamed toward the palace as night fell, crossing a no-go zone set up around the compound's perimeter.
There was no visible violence, but tensions were high after clashes at the same spot on Wednesday between pro- and anti-Morsi supporters left seven people dead and more than 600 injured.
Several army tanks were stationed in the square and nearby but made no movement against the protesters, some of whom clambered atop them to declare the army was "hand in hand" with them.
That was reminiscent of the popular uprising that ousted long-time president Mubarak early last year, when tanks stood idle amid massive protests in Cairo's Tahrir Square, as protesters mixed with soldiers.
The crowd also shouted "We want to see the fall of the regime" - a slogan common during the anti-Mubarak revolt.
Calls to step down
The increasingly strident calls for Morsi to step down followed an address on Thursday in which the president dismissed demands he give up sweeping new powers he decreed for himself two weeks ago and postpone a December 15 referendum on a constitution drafted by a panel of Islamist allies.
Leaders of the main opposition group, the National Salvation Front, rebuffed a grudging offer from Morsi to talk with them about the political crisis his decisions have triggered.
Both Morsi's Islamist backers and the largely secular opposition have dug in their heels in the confrontation, raising the prospect of further escalation.
In his speech, Morsi sought to portray elements of the opposition as "thugs" allied to remnants of Mubarak's regime.
The Front shot back, accusing the president of "dividing Egyptians between his 'supporters of legitimacy'... and his opponents."