"Houthi aggressors, out of the capital," went one chant, and "Hadi, Hadi, return. Your people are awake," said another. One slogan accused the Houthis, who adhere to a sect of Shiism, of being clients of mostly Shiite Iran, while another said they were colluding with Hadi's predecessor, longtime autocrat Ali Abdullah Saleh.

Security officials who spoke on condition of anonymity because they were not authorized to brief reporters, said tens of thousands also demonstrated in the cities of Taiz, Ibb and Dhamar with similar demands.

In Dhamar, protesters formed a human chain, demanding the "restoration of the state." Many across the country described the Houthi power grab as a "coup." The Houthis, who say they are fighting corruption, said in a statement Friday night that they would work to bring about a smooth, democratic transfer of power after the resignations.

The Houthis, who captured several cities as they drove south from their northern strongholds last summer, seek greater representation in government ministries and on a committee to rewrite the country's constitution. They now face mounting pressures and internal divisions however, and there have been signs they do not want to rule the country outright and would prefer that Hadi remain as a figurehead president.

Ali al-Bukhaiti, a prominent member of the group's political arm, resigned Friday over what he described as a dangerous political polarization that could turn regional and secular and eventually break up the country. He offered to work as a mediator between the groups.

The national parliament meets Sunday to consider Hadi's resignation. Should it be accepted, or should Hadi simply refuse to rule, law dictates that the job would go to Parliament Speaker Yahia al-Rai -- a close Saleh ally.