The Yemeni foreign minister has called for Gulf Arab states to intervene to prevent the advance of Shia Houthi rebels into the south of the country.
The Houthis ousted President Abdrabbuh Mansour Hadi last month, who fled to the southern port city of Aden where he established a rival power base.
At the weekend, the Houthis seized Taiz, Yemen’s third largest city, bringing them closer to Aden.
The UN has warned that Yemen is on the edge of civil war.
Mr Hadi’s Foreign Minister Riad Yassin told the Saudi-owned Asharq al-Awsat newspaper he asked the six-nation Gulf Cooperation Council (GCC) to intervene, without elaborating what that would mean.
He also said he had asked the UN and GCC to impose a no-fly zone, after warplanes hit the presidential palace in Aden over the weekend.
The Houthis’ rise has alarmed the GCC, and in particular Sunni-controlled Saudi Arabia, which accuses the Houthis of being a proxy for their key regional rival, Shia-majority Iran. Both of them have denied the Saudi claims.
Also on Monday, the Saudi foreign minister warned the Gulf states could take action to shore-up Mr Hadi.
The Houthis: A minority Shia from the north, the group seized control of Sanaa last year and have since been expanding their control.
President Hadi: Backed by military and police loyalists, and by militia known as Popular Resistance Committees, he is trying to fight back against the rebels from his stronghold in the south.
Al-Qaeda in the Arabian Peninsula: Seen by the US as the most dangerous branch of Al-Qaeda, AQAP opposes both the Houthis and forces loyal to President Hadi.
Islamic State: A Yemeni affiliate of IS has recently emerged, which seeks to eclipse AQAP.
“If this issue is not solved peacefully, we will take the necessary measures to protect the region from their aggression,” said Saud al-Faisal.
The UN envoy to Yemen, Jamal Benomar told the BBC the Saudis had “good reasons” to be concerned about the situation.
But he added: “I don’t think any side could win a civil war. No side can win a civil war – the only way forward is negotiation, which implies concession from all sides, which implies also, a compromise.”
Britain has meanwhile joined the US in withdrawing special military forces from Yemen because of the deteriorating situation there.
Further deepening the crisis, Islamic State (IS) militants appear to have emerged as a presence in Yemen.
A purported local IS affiliate says it was behind an attack that left 29 dead in Lahj, north of Aden, after another branch claimed the suicide attacks last week in Sanaa that left more than 100 people dead.