SANAA, Yemen -- The embattled Yemeni leader who resigned the presidency last month and has fled the rebel-controlled capital said on Sunday that he is still the country's legitimate president and is ruling from the south.

The surprise move to withdraw his resignation and challenge the Shiite rebels known as Houthis raised the stakes in Yemen's political deadlock, fanning fears that the strategically located country could now face a regional split.

"Abed Rabbo Mansour Hadi exercises his functions as president of the republic in Aden with legitimacy not subject to questioning," his office said in a statement after he met with governors from all six southern provinces and received their backing.

The meetings were in the southern city of Aden, where Hadi arrived on Saturday and said that all actions taken since the rebels stormed the capital Sanaa last September were illegitimate. Aside from the southern provinces, three northern ones -- Marib, Jawf and the country's largest in terms of population, Taiz -- also lent him their support in statements.

Hadi's aides have said that since he made his resignation under house arrest, with rebels controlling the capital and without the legally required ratification by parliament, it was invalid. The rebels had first prevented the parliament from meeting and then dissolved it earlier this month.

On Sunday the Socialist, Leftist, Nasserist, Salafi and Islamist Islah parties threw their weight behind Hadi's cause, issuing statements endorsing his return to power. Tens of thousands also marched in anti-Houthi protests and in support of Hadi in the cities of Taiz, Ibb and Houdeida.

The largest party in Yemen however, the General People's Congress of Hadi's predecessor Ali Abdullah Saleh, rejected Hadi's move to reclaim office.

Hadi has called on the Houthis to leave the capital and for the military and security forces to rally to his side.

Yemen's Gulf Arab neighbours have warned that if the world fails to act against the rebels, they will take whatever actions deemed necessary to maintain regional security and stability.

Egypt has set up a special rapid deployment force that could intervene if the Houthis threaten shipping lanes.