Tens of thousands packed Cairo’s Tahrir Square yesterday as Islamists flexed their political muscle in perhaps Egypt’s largest protest since a popular revolt overthrew President Hosni Mubarak in February.

Islamists from across the country flocked into the central square to defend what they called “Egypt’s Islamic identity” and to demand that parliamentary elections take place as scheduled by the end of the year.

The rally, organised by hardline Salafi groups and the influential Muslim Brotherhood, came as tensions grow between secular activists and the military on the one hand and Islamists on the other.

“The people demand the application of God’s law,” thousands chanted under the searing sun, many of them carrying umbrellas or pouring water on their heads to counter the heat.

The rally officially started after the Muslim noon prayer, but thousands had already made their way to the square overnight and by morning chants calling for an “Islamic state” rang across Tahrir.

Islamist groups have been organising the rally for weeks, sparking fears of clashes with secular protesters who have been camped out in the square since July 8.

After two days of meetings, the secular and Islamist groups agreed to try to put their differences aside and focus on the common goals in order to save the revolution that toppled Mr Mubarak, organisers said.

But the agreement quickly unravelled with more than two dozen groups announcing their withdrawal from the protest because of the Islamist slogans.

“We had an agreement that it would be a day of unity, but it turned into something else,” said Mohammed Waked, a member of the Front for Justice and Democracy.

The sheer size of the protest appeared to have intimidated secular activists, some of whom took to Twitter to deride the protest as “Tahriristan.”