Clashes rocked the Yemeni capital on Saturday after 37 people were killed in 24 hours despite calls by President Ali Abdullah Saleh for peace after his return from months of medical treatment in Riyadh.
"We slept and woke up to the non-stop sound of gunfire," one Sanaa resident told AFP as firefights between rival military units raged in the city centre.
Republican Guard troops, commanded by Saleh's son Ahmed, have been locked in a week of deadly battles with dissident soldiers from the First Armoured Brigade headed by General Ali Mohsen al-Ahmar, who have since March protected anti-regime protesters camped out on Sanaa's Change Square.
Security forces have also been fighting supporters of dissident tribal chief Sheikh Sadiq al-Ahmar in Sanaa's northern Al-Hasaba district.
The fighting has caused 132 deaths since Sunday, based on a tally obtained from medics and tribal and opposition sources. State news agency Saba said 24 of Saleh's soldiers have also been killed.
Troops loyal to Saleh killed at least 17 people in an attack launched just after midnight on Friday, shelling and firing on Change Square which protesters first occupied in February.
"Seventeen people were killed and 55 others were wounded,"said Mohammed al-Qabati, a medic at the field hospital in the square.
Among the dead were dissident soldiers, while the rest were civilians, Qabati told AFP without providing specific figures.
Snipers also opened fire from buildings around the square, witnesses said.
Tens of thousands of people remained camped in the square even after Republican Guard troops burned down several of their tents, witnesses said.
In the north of the city, fighting continued between Saleh's troops and Sheikh Sadiq supporters in Al-Hasaba, residents said, reporting the sound of automatic weapons fire and explosions.
Saleh returned to Yemen on Friday, preaching peace, after a three-month absence in Saudi Arabia, where he was treated for wounds sustained in an attack on his palace on June 3.
Tens of thousands of his supporters gathered in the capital's Sabiin Square near his palace to celebrate his return at the main weekly Muslim prayers.
"I have returned home carrying the dove of peace and an olive branch, not holding any grudges or hatred towards anyone," Saba quoted Saleh as saying.
He urged all Yemenis to "overcome their pain and wounds for the sake of the nation and its dignity."
But in north Sanaa, tens of thousands of his opponents attended a mass funeral of 40 people killed in the recent clashes and vowed to bring Saleh to trial.
"The people want to bring the slaughterer to justice," they chanted.
"We thank Saudi Arabia for returning Ali to us so we can bring him to trial inside the country," said activist Mohammed al-Asal.
A spokesman for the ruling General People's Congress party, Tariq al-Shami, told AFP that "no public appearance or political activity" has yet been scheduled for Saleh.
But Saba said the president would make "an important speech to mark the 49th anniversary" of the September 26, 1962 revolution which saw Yemen proclaimed a republic.
Traditionally Saleh, who has been in power since 1978, makes his speech on the eve of the anniversary, but Saba did not specify when it would happen this year.
Even as the 69-year-old Saleh called for a ceasefire and talks, the United States urged him to step down, with the White House calling on him to begin a "full transfer of power."
"In light of the current instability in Yemen, we urge President Saleh to initiate a full transfer of power and arrange for presidential elections to be held before the end of the year within the framework of the GCC initiative," spokesman Jay Carney said.
A senior Saudi official told AFP Saleh had returned from Riyadh to put his house "in order" and "prepare for elections."
Saleh will "leave" after this, the official added, without specifying whether he would leave Yemen altogether or only leave power.
Yemen's wealthy Gulf neighbours have been trying for months to persuade Saleh to accept a plan under which he would transfer power in return for a promise of immunity from prosecution.
But the latest mediation mission by Gulf Cooperation Council chief Abdullatif al-Zayani foundered amid fighting in Sanaa, and he flew out on Wednesday empty-handed.