Tens of thousands of protesters packed Cairo's downtown Tahrir Square on Friday in the biggest demonstration in months against the ruling military, aimed at stepping up pressure on the generals to hand over power to civilians and bar ex-regime members from running in upcoming presidential elections.

Both Islamists and liberals turned out in force for the protest, to show the widespread anger at the military over the country's political chaos ahead of the first presidential elections since the fall of Hosni Mubarak more than a year ago. The confusion has raised suspicions the generals — ruling since Mubarak's ouster — are manipulating the process to preserve their power, to ensure the victory of a pro-military candidate and prevent reform.

"Down with military rule," protesters in Tahrir chanted, and banners draped around the sprawling plaza denounced candidates seen as "feloul," or "remnants" from Mubarak's regime.

But the crowds in Tahrir were divided between rival groups with differing complaints and goals. As a result, the participants failed to reach a unified list of demands.

Liberals and youth groups called for all factions to agree on an anti-military "revolution" candidate in the presidential vote, but the powerful Muslim Brotherhood and other Islamists — who have their own ambitions in the race — refused to sign on.

The Brotherhood, Egypt's strongest political movement, has been frustrated that the military has prevented their domination of parliament from translating into real political power. The group was angered when the military-appointed election commission over the past week disqualified its initial candidate for president, along with nine other hopefuls.

In response, the Brotherhood is calling for a "second revolution."

Brotherhood largely stayed out of protests

Liberals and the youth groups who led the revolt against Mubarak, however, are skeptical, accusing the Brotherhood of abandoning the revolution the past year to pursue their own quest to rule. The Brotherhood largely stayed out of anti-military protests since Mubarak's fall and accepted the generals' running of the transition, betting that the process would pave their way to political power.

Many in the secular camp demand the Brotherhood "apologize" for its actions the past year and show it is not intent on monopolizing power.

'We came to demand that presidential elections take place on time, without delay even for a single day' —Muzhar Shahine, Muslim cleric

Khaled al-Balshi, editor of the leftist Al-Badeel news site, said he feared that Islamists are once again using the protests as a card to pressure the military council and would go back to striking deals with it again later.

"I am afraid that right now there is something being cooked," he told Al-Jazeera television.

Another major force in the square were the ultraconservative Salafis, an Islamic movement that is more hard-line than the Brotherhood. Many of them are furious over the disqualification of their favoured presidential candidate, Hazem Abu Ismail, who was barred from the race because his mother held American citizenship. Election rules bar a candidate's close family from having foreign citizenship. Many of his supporters accuse the military and election of commission of forging documents to force out the popular Abu Ismail.

His supporters marched through the square Friday carrying a long banner with Abu Ismail's image, demanding that he be reinstated.

Transfer to civilian power by early July

The presidential elections are scheduled for May 23-24. A new president will be announced on June. 21. The military council has pledged to transfer power to the elected civilian administration by early July.

Members of military council spoke more than once over the past weeks assuring that they don't intend to postpone elections and they are not in favour of any candidate.

But the council raised worries that they intend to push back the election and hold power longer when the generals said in a closed-door meeting with political parties that they believe the writing of Egypt's new constitution should be finished before a president is seated. The constitution-writing process is already in turmoil, and few believe it could be completed in that time frame.

"Today we came to demand that presidential elections take place on time, without delay even for a single day," Muslim cleric Muzhar Shahine told protesters in a Friday sermon in Tahrir. "Let's forget the mistakes of each other ... for the sake of our nation's interest," he said.

But the divisions were evident in Tahrir. Each faction rallied around its own stage in the square, each with its own speeches and slogans blaring over loudspeakers.