Shiite militiamen who seized power in Yemen vowed to defy "threats" as the UN Security Council prepared to adopt a resolution calling on them to step aside or face consequences.
Yemen is a traditional US ally in the fight against Al-Qaeda, but the impoverished Arabian Peninsula country has descended into chaos since the militia known as Huthis overran the capital in September.
In another city they captured last year, Ibb in central Yemen, Huthis fired on hundreds of protesters to disperse them today, wounding several.
Militiamen also clashed with Sunni tribes east of the central city of Baida which the Huthis have been trying to overrun as they extend their influence.
Tribal sources said at 12 Huthis were killed, but there was no independent confirmation of the toll.
On February 6, the Huthis ousted the government and dissolved parliament, tightening their grip after Western- backed President Abedrabbo Mansour Hadi resigned in protest at their advance.
UN 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 Huthis to withdraw from government and security institutions "immediately and unconditionally".
It also urges them to "engage in good faith in the UN-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, which is already under US and European sanctions over its annexation of Crimea and backing of rebels in eastern Ukraine, was reluctant to vote for sanctions.
It is the council's first resolution on Yemen since the Huthis grabbed power last week in a move the United States and Gulf Arab countries described as a "coup".
The six-nation Gulf Cooperation Council yesterday urged the UN 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 neighbouring Yemen fail to resolve their differences, without elaborating.
The 57-member Organisation of Islamic Cooperation (OIC) voiced support today for the GCC statement and condemned the Huthi "coup".
Huthi spokesman Mohammed Abdulsalam, 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 Huthis to relinquish power and criticised the withdrawal of ambassadors.
