CAIRO — A massive crowd of tens of thousands calling for the ouster of President Hosni Mubarak is gathering in the streets and squares of downtown Cairo in a peaceful demonstration and they are vowing to defy a curfew that is to go into force in less than an hour.

There is only a light military presence — a few tanks — and soldiers are not intervening.

No police were seen in the crowds and no clashes were reported.

One army captain joined the demonstrators, who hoisted him on their shoulders while chanting slogans against Mubarak.