By Michelle Nichols
UNITED NATIONS, March 22 (Reuters) - The United Nations Security Council will on Sunday condemn the takeover of much of Yemen and its institutions by the Shi'ite Muslim Houthi militia and warn of "further measures" if hostilities do not end, diplomats said.
In a statement that will be formally adopted at a meeting on Yemen later on Sunday, the 15-member body also stated its support for Yemen's President Abd-Rabbu Mansour Hadi, the diplomats said on condition of anonymity.
Yemen has been hurtling towards civil war since last year when the Iran-allied Houthis seized Sanaa and advanced into Sunni Muslim areas, leading to clashes with local tribes and energising a southern separatist movement.
Earlier on Sunday, Houthis took over the central city of Taiz in an escalation of a power struggle diplomats say risks drawing in neighboring oil giant Saudi Arabia and its main regional rival Iran.
Their advance comes a day after nearly 140 worshippers died in suicide bombings of two mosques in Sanaa that are used by the Houthis. The attacks were claimed by Islamic State.
The Security Council "condemns the ongoing unilateral actions taken by the Houthis, which undermine the political transition process in Yemen, and jeopardize the security, stability, sovereignty and unity of Yemen," the statement will say, according to the diplomats.
The council will urge "non-state actors to withdraw from government institutions, including in the south of Yemen, and to refrain from any attempt to take over such institutions."
The statement also threatens "to take further measures against any party" to the conflict in Yemen. In November, the council imposed sanctions on Yemen's former president, Ali Abdullah Saleh, and two Houthi leaders.
Hadi, who operates from the southern port city of Aden since fleeing Houthi house arrest in Sanaa, has asked the Security Council for urgent help "in all available means to stop this aggression."
U.N. mediator Jamal Benomar is likely to brief the council later on Sunday via video link and the ambassadors of Yemen and Qatar, as chair of the Gulf Cooperation Council that comprises Gulf Arab states, will also speak, diplomats said
Yemen is home to Al Qaeda in the Arabian Peninsula, one of the global network's most active arms, which has carried out attacks abroad.
The Security Council expressed concern that al Qaeda could benefit from the deterioration of the political and security situation in Yemen.
(Reporting by Michelle Nichols; Editing by Raissa Kasolowsky)
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