President Abdrabuh Mansur Hadi warned Tuesday of "civil war" in Sunni-majority Yemen and vowed to restore state authority as Shiite rebels in apparent near-total control of Sanaa hailed their "victory".
Yemen "is facing a conspiracy" and "the danger of slipping into civil war", Hadi said in a speech at the presidential palace, two days after Ansarullah rebels took all other key state institutions in the capital, overshadowing a UN-brokered peace deal.
In a televised speech, rebel leader Abdelmalek al-Huthi hailed what he called the "victory" of his fighters.
"We congratulate our people on the victory of their popular revolution that has established a new era based on cooperation," Huthi said.
Hadi had earlier evoked the spectre of foreign plots aimed at torpedoing progress in Yemen.
"Internal and foreign forces (have) allied to... overthrow the Yemeni model" of power transition following an Arab Spring-inspired uprising, the president said.
Yemen was the only Arab Spring country where an uprising led to a political settlement by which Hadi replaced former autocrat Ali Abdullah Saleh.
Hundreds of rebels manned checkpoints on the airport road and other major throughfares on Tuesday while heavily armed patrols cruised the streets in four-wheel-drive vehicles, AFP correspondents reported.
- 'Sanaa will not fall' -
Insurgents alongside small detachments of military police guarded public offices the rebels entered on Sunday, including the main government building, parliament, army headquarters and the central bank.
But Hadi insisted: "Sanaa will not fall."
UN envoy Jamal Benomar, who mediated the accord aimed at ending deadly fighting between the rebels and Sunni Islamists, said the rebels' taking of key institutions virtually without resistance seemed to signify the "collapse" of the security forces in Sanaa.
"What has happened these past few days could lead to the collapse of the Yemeni state and the end of the political transition," he told Al-Arabiya television late Monday.
As Benomar spoke, the peace accord appeared to be holding after a week of clashes that the government said killed at least 200 people.
Yemeni authorities have repeatedly accused Iran of backing the Huthi rebels, who also appear heavily influenced by Hezbollah, Lebanon's powerful Shiite militia that is backed by Tehran.
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Ansarullah waged a decade-long insurgency in the mountainous north before launching a bid for power in Sanaa last month.
Sunday's UN-brokered deal aims to put the troubled transition back on track in impoverished Yemen, which borders oil kingpin Saudi Arabia and is a key US ally in the fight against Al-Qaeda.
The speed of the rebel advance reflected the fragility of Yemen's regime three years after the uprising.
"You were shocked to learn that public and military institutions were handed over (to rebels), but be aware that the plot was already brewing," Hadi told Yemenis Tuesday.
- Saleh's involvement 'unclear' -
Saleh is himself a Zaidi Shiite, a community which forms 30 percent of Yemen's mostly Sunni population but is the majority in the northern highlands, including Sanaa province.
He was repeatedly accused by his opponents of impeding the transition.
"There is no doubt that Saleh has facilitated Huthi expansion in and around the capital," April Longley Alley, a specialist on Yemen with the International Crisis Group, told AFP.
"At the very least he has not discouraged his tribal and political supporters from supporting Huthi mobilisation."
However, "the extent of his involvement is unclear", she told AFP.
Under Sunday's deal, Hadi had three days to bring a rebel representative into government as an adviser and to name a neutral replacement for prime minister Mohamed Basindawa.
Before the deal was struck, Basindawa tendered his resignation as the security forces surrendered state institutions without a fight, although it has yet to be formally accepted.
A security protocol to Sunday's agreement requires the rebels to hand over the institutions they have seized, and once a new premier has been named, to start dismantling armed protest camps in and around Sanaa.
Rebel representatives refused to sign the security protocol on Sunday.
The deal also requires Hadi to appoint an adviser from the separatist Southern Movement which has been campaigning for the secession of the formerly independent south, another major obstacle to stability.