Raging battles between heavily armed loyalists and foes of Yemen's president killed ten people in the capital as a crisis over a violent state crackdown on popular unrest drifted towards civil war.
Gunfire appeared to have stopped in the afternoon but both the opposition and the government vowed to defend themselves against any perceived aggression in a city they have divided between themselves into areas of control.
At least 68 people have been killed since Sunday when frustration boiled over at President Ali Abdullah Saleh's refusal to accept a mediated power transfer plan after suffering serious wounds in a June assassination attempt.
Opposition and government sources said they were in talks on a political solution to the crisis.
A Western diplomat told Reuters mediators were trying to hang on to the positive direction negotiations had been heading only a few days earlier.
"All the evidence is that we are continuing with Yemeni politics and conflict as usual. They will sit down and talk, but without a deal, it will kick off again in the future," the diplomat said.
Heavy shelling and machinegun fire rocked Sanaa before dawn on today and snipers lurked in the upper stories of buildings near the site now called "Change Square" where protesters have camped out to demand an end to Saleh's 33-year rule.
Four defector soldiers were killed in street fighting with pro-Saleh forces and two civilians died when three rockets crashed into a protest camp just after morning prayers.
Government officials and opposition groups have traded accusations over who was responsible for the violence of the past two days of which activists at Change Square, who number in the thousands, were the main victims.
But a consensus was emerging among sources on all sides that government forces clashed with those of defected General Ali Mohsen, who has pledged to defend the activists, after his men took control of territory previously under government control.
The opposition said Gen Mohsen's troops took the area to fend off security forces they believed would enter the protest camp.
A witness close to the protest camp said Yemen's Republican Guard forces had fired from an army site on a mountain and shelled Mohsen's First Armoured Division compound.
The protesters may have been hit by stray projectiles, he said.
A source at Mohsen's office said his forces were holding off at the request of Saleh's Vice President Abd al-Hadi Mansour but warned that protesters would be harder to control.
"I don't think the youth protesters can be reined in until this regime leaves power," the source said.
Some 400 protesters have been killed since protests began in January.
