SANAA: Shiite militiamen who seized power in Yemen vowed to defy “threats” as the U.N. Security Council prepared to adopt a resolution Sunday calling on them to step aside or face consequences.

Yemen is a traditional U.S. ally in the fight against Al-Qaeda, but the impoverished Arabian Peninsula country has descended into chaos since the militia known as Houthis overran the capital in September.

In another city they captured last year, Ibb in central Yemen, Houthis fired on hundreds of protesters to disperse them Sunday, wounding several people.

Militiamen also clashed with Sunni tribes east of the central city of Baida, which the Houthis have been trying to overrun as they extend their influence.

Tribal sources said at 12 Houthis were killed, but there was no independent confirmation of the toll.

The Houthis on Feb. 6 ousted the government and dissolved parliament, tightening their grip after Western-backed President Abed Rabbou Mansour Hadi resigned in protest at their advance. U.N. Secretary-General Ban Ki-moon has warned that Yemen is falling apart and called for Hadi’s reinstatement.

Citing security concerns, nine Arab and Western countries shuttered their embassies in Yemen last week and evacuated diplomats.

The Security Council is expected to adopt a resolution calling on Houthis to withdraw from government and security institutions “immediately and unconditionally.”

It also urges them to “engage in good faith in the U.N.-brokered negotiations” led by special envoy Jamal Benomar and to release Hadi, Prime Minister Khalid Bahah, and other officials and activists under de facto house arrest or in detention.

Western diplomats said Russia was reluctant to vote for sanctions.

It is the council’s first resolution on Yemen since the Houthis grabbed power last week in a move the United States and Gulf Arab countries described as a “coup.”

The six-nation Gulf Cooperation Council Saturday urged the U.N. to evoke Chapter Seven of the United Nations Charter, which allows for economic and military pressure to enforce Council decisions.

They said they themselves would act if the rival factions in neighboring Yemen fail to resolve their differences, without elaborating.

The 57-member Organization of Islamic Cooperation voiced support Sunday for the GCC countries’ statement and condemned the Houthi “coup.”

And the Arab League said it would hold an emergency meeting on Yemen Wednesday.

Houthi spokesman Mohammad Abdel-Salam, quoted by the official Saba news agency which the militia controls, insisted that “the Yemeni people won’t cede power in the face of threats.”

He denounced as “provocative blackmail” demands for the Houthis to relinquish power and criticized the withdrawal of ambassadors.

In their bid to establish authority across Yemen, the militiamen have tried to stifle opposition and have been accused of detaining and torturing opponents.

They announced a ban on anti-Houthi protests last week.

Ahmad Hazzaa, a leader of the anti-Houthi Rafdh (rejection) Movement, was detained Saturday by Shiite militiamen, members of his group told AFP.

Meanwhile political forces and governors of three southern provinces – Aden, Lahij, and Mahra – formed a local “administrative, security, and political leadership rejecting the coup” by the Houthis.

In a statement issued at the end of a meeting in the south’s main city Aden, leaders of the three provinces demanded Hadi’s reinstatement and affirmed their support for Yemen becoming a federation based on the outcome of a national dialogue held last year.