CAIRO — Hundreds of thousands of Egyptians flooded downtown Cairo on Tuesday in the biggest and most dramatic show of opposition to Egyptian President Hosni Mubarak since protests began eight days ago.

The chant of the day was “leave,” but the mood was festive, and there were no immediate reports of violence.

The crowd filled Tahrir or Liberation Square and packed the streets leading into it as far as the eye could see.

Protesters strung up an effigy of Mubarak, hung a banner which said, in English, "The people demand the removal of the regime." They also displayed altered posters of Mubarak, showing him with a Hitler mustache.

Whole families turned out, and in many cases, whole neighborhoods to demand an end to Mubarak’s 30 years of rule. Also joining them were famous Egyptian actors and singers. There was a contingent of clerics, chanting, and also Christian priests in the crowd.

Whenever a low-flying police helicopter would buzz the crowd, protesters would start the chant: “Leave. Leave.”

The Egyptian army stationed tanks at the corners of the square but did not interfere with the demonstration. There were no police in sight.

At every entrance to the square, citizen groups set up checkpoints, checked ID’s and did pat-downs of protesters to ensure no one was carrying a weapon.

The day began with plans to march on the presidential compound. But, there was an abrupt change because of roadblocks, so protesters decided to stay in the square and build a critical mass.

There was no sign that Mubarak would heed the demands of the street. State television broadcast a photo of the main bridge and the national museum, but from an angle that avoided showing the crowds. State television, which Mubarak controls, was broadcasting call-in messages from citizens praising Mubarak and saying the country needed to keep him in power.