Shiite rebels held position Monday around key government offices and army bases in the Yemeni capital which they captured without resistance just hours before the signing a UN-brokered peace agreement.
Sunday's hard-won deal, signed by the president and all the main political parties, is intended to end a week of deadly fighting in Sanaa between the rebels and their opponents, and put the country's troubled transition back on track.
The impoverished Arabian Peninsula country borders oil kingpin Saudi Arabia and is a key ally of Washington against what it regards as Al-Qaeda's most dangerous affiliate.
But just hours before the signing, the rebels took control of the government building, parliament and army headquarters in a lightning offensive that met little or no resistance.
The speed of the advance reflected the fragility of the regime and the persistent divisions within the armed forces three years after a deadly uprising which forced veteran strongman Ali Abdullah Saleh from power.
Rebel fighters were manning joint checkpoints with troops outside the public offices under their control, AFP correspondents reported.
The interior ministry had called on the security forces on Sunday not to confront the rebels.
The rebels brought reinforcements into the capital overnight from their strongholds further north, tribal sources said.
Sanaa mayor Abdulqader Hilal resigned in protest late on Sunday after rebels seized his car at a checkpoint, sources close to him said.
Under Sunday's deal, President Abdrabuh Mansur Hadi has three days to bring a rebel representative into government as an adviser and to name a neutral replacement for prime minister Mohamed Basindawa who quit on Sunday.