Ousted president Abed Rabbo Mansour Hadi later arrived in Aden but planned to travel on for medical treatment, the aides revealed.
Hadi has been under house arrest for weeks following a coup by Shiite Houthi rebels who captured Sanaa in September.
The aides said the rebels let Hadi go after pressure from the United Nations, the United States, Russia and local political parties.
Witnesses said Houthis and others in the area later ransacked Hadi’s house and at least three people were seen carrying Kalashnikov assault rifles taken from the property.
Jamal Benomar, the UN envoy to Yemen, said on Friday that rival factions, including the Houthis, had agreed on a new legislative body made up of former and serving parliamentarians to form a transitional government. But a coalition of Yemeni parties voiced objections to the plan, describing it as an inadequate half-way house.
Ahmed Lakaz, of the Unionist Gathering Party, taking part in the dialogue, said the parties told the Houthis they would drop out of the process if Hadi was not freed.
Yemen has been locked in a political crisis since the Houthi rebels took over Sanaa and forced the resignation of the elected pro-western Hadi and dissolved the parliament while keeping the ousted president under house arrest.
The crisis cast doubt on America’s ability to continue counter-terrorism operations in Yemen, though it has continued to target al-Qaeda’s branch in Yemen, known as al-Qaeda in the Arabian Peninsula (Aqap), with drone strikes.
Thousands marched yesterday in support of Hadi in southern Ibb province, and urged the Houthis to get out of the region and stop meddling.