Thousands of demonstrators waved red cards in Tahrir Square Sunday to demand the resignation of Egypt's Islamist President Mohamed Morsi, as the spirit of 2011's revolution returned to the iconic Cairo protest venue.

"The people want the ouster of the regime!" protesters chanted -- the signature slogan of the uprising that ousted Hosni Mubarak and brought Morsi to power.

Jubilant men, women and children brandished red cards, blowing whistles and vuvuzelas and chanting "Leave, Morsi!"

"This is the second revolution and Tahrir is the symbol of the revolution. The revolution will be launched from here," said Ibrahim Hammouda, a carpenter who had came from the northern city of Damietta to join the protests.

In 2011, when hundreds of thousands of people took to the streets to end Mubarak's authoritarian three-decade rule, they held up posters of regime figures with their faces crossed out.

This time, protesters are holding pictures of senior leaders of the Muslim Brotherhood, from which Morsi hails.

Morsi was elected a year ago in Egypt's first ever free vote. But today, his critics accuse him of betraying the revolution by concentrating power in the hands of Islamist groups.

They accuse him of breaking his promise to be a president "for all Egyptians" and letting the economy dive into free fall.

"I'm here because Morsi, who I voted for, betrayed me and did not keep his promises. Egypt will be liberated again from Tahrir Square," said Mohammed Samir who travelled from the Nile Delta city of Mansura.

The Tahrir protest began hours before scheduled rallies and marches due to begin at 5:00 PM (1500 GMT), with several hundred people having spent the night in the square.

Street vendors sold flags and patriotic songs boomed from loudspeakers.

On the outskirts of the square, security checkpoints were manned by protesters in fluorescent vests under signs reading: "No entry to the Brotherhood".

"We are protecting the revolution from those who are against the revolution," said protester Essam Ahmed.

On the other side of Cairo, in the Nasr City neighbourhood, thousands of pro-Morsi supporters gathered to show support for the president.

They insist that ousting an elected president would be a coup against democracy that they will not allow.

Egypt is deeply divided between Morsi's mainly Islamist supporters and a broad-based opposition that also includes many deeply religious Muslims.

"Morsi, you hypocrite, you have split the people in two!" the protesters chanted in Tahrir.

The Muslim Brotherhood was long banned under Mubarak's regime, but since the revolution they have dominated parliament, drafted a controversial constitution and been given key cabinet and local government positions.

"The Brotherhood did not continue our revolution and insisted on monopolising the state," said Mohammed Abdel Wahab, a marketing manager from Cairo who came to Tahrir with his family.

Sunday's protests were called by Tamarod (Arabic for Rebellion), a grassroots campaign that says it gathered more than 22 million signatures calling for Morsi to go and for a snap presidential election.