Global powers have been pressing Saleh to sign a Gulf-led deal to handover power to try to stem the growing chaos in Yemen, home to al Qaeda militants and neighbor to the world's biggest oil exporter, Saudi Arabia.
"The ceasefire agreement has ended," a government official said Tuesday adding that tribal groups have gained control of a government building.
Overnight battles in the capital brought an end to the truce brokered at the weekend. More than 115 people were killed last week in urban battles with machine guns, mortars and rocket propelled grenades in the bloodiest fighting since anti-government protests began months ago.
In the capital Sanaa, several explosions were heard over the staccato of machine guns in the district of Hasaba, the scene of week-long fighting between Saleh's forces and tribesmen.
"Last night's clashes were the fiercest so far, my children and I couldn't sleep all night because of the heavy shooting," Mohammed al-Quraiti, a Hasaba resident, told Reuters.
The fighting last week between members of the powerful Hashed tribe led by Sadeq al-Ahmar and Saleh's security forces widened to areas outside the capital where tribesmen squared off against Saleh's elite Republican Guard.
Opposition forces have called for nationwide protests later Tuesday. Saleh's forces this week broke up similar protests in Taiz, about 200 km (120 miles) south of the capital, by firing on crowds and running over demonstrators with bulldozers, killing at least 15 and wounding hundreds.
In an ominous sign, residents said soldiers had again opened fire on protesters in Taiz Tuesday. Medical sources said at least three people have been killed so far.
FIGHTING WITH AL QAEDA
Further south, government troops and locals have been trying to force al Qaeda and Islamist militants from the coastal city of Zinjibar after they seized the town at the weekend.
Saba news agency reported Tuesday that 21 Yemeni soldiers had been killed a day earlier in the clashes where Yemen's air force dropped bombs on the city of 20,000 near the Gulf of Aden.
Residents said bodies were strewn on the streets, the national bank building was burned and explosions rocked the city from which most people have fled.
"Explosions lit the sky. One shell fell in the street at the back of my house where militants were stationed," one resident said.
The United States and Saudi Arabia, both targets of attacks by Yemen-based al Qaeda in the Arabian Peninsula, are worried that chaos is emboldening the group.
Opposition leaders have accused Saleh of deliberately allowing Zinjibar, near a sea lane where about 3 million barrels of oil pass daily, to fall to al Qaeda to try to show how chaotic Yemen would be without him.
Opposition groups made up of tribal leaders, Islamists and leftists have said they could do a far better job of curtailing the al Qaeda threat.
At least 320 people have been killed in various fighting in Yemen since protests calling for Saleh to end his nearly 33 year rule started about four months ago, inspired by the popular uprisings that ended the reign of the long-standing rulers of Tunisia and Egypt.
Under Saleh, Yemen has moved to the brink of financial collapse, with about 40 percent of the population living on less than $2 a day and a third facing chronic hunger.