The deal included a withdrawal of armed tribesmen from government buildings and moves to normalize life in the Hasaba district of the capital Sanaa, scene of a week-long clash that killed 115 people.

A government official said: "Yes, we have an agreement which takes effect tomorrow (Sunday) morning."

A tribal official confirmed an agreement had been reached.

The fighting had prompted thousands of residents to flee Sanaa and raised the prospect of chaos that could benefit the Yemen-based branch of al Qaeda and threaten neighboring Saudi Arabia, the world's biggest oil exporter.

The latest violence, pitting Saleh loyalist forces against members of the powerful Hashed tribe led by Sadeq al-Ahmar, was the bloodiest since pro-democracy unrest erupted in January and was sparked by Saleh's refusal to sign a power transfer deal.

Mediators will start taking over the occupied buildings from the al-Ahmar tribesmen on Sunday and hand them over to government forces, the mediators said.

In southern Yemen, three French aid workers went missing and a local security official said they were believed to have been abducted.

Kidnappings of Western tourists or workers by disgruntled tribes seeking ransom or concessions from the government have been frequent in Yemen. Most hostages have been freed unharmed.

A prominent think-tank, the International Crisis Group, said a broad, lasting ceasefire was needed immediately and should be part of a plan that leads to a transition of power.

The political crisis has already cost the economy as much as US$5 billion and immediate aid is needed to prevent a meltdown in the country with a nominal GDP of US$31 billion, the country's trade minister said.

On Friday, Yemeni tribesmen said they had captured a military compound from elite troops loyal to the president 100 km (60 miles) outside Sanaa, widening a conflict hitherto concentrated mainly in the capital near the home of Ahmar.

The fighting has overshadowed a largely peaceful protest movement that started months ago aimed at ending Saleh's 33-year-long autocratic rule and inspired by uprisings that brought down the long-standing leaders of Tunisia and Egypt.