Six Yemenis were killed on Saturday in shelling by government forces of the country's second city of Taez and in shootings, as sustained violence threatened to derail a fragile power-transfer deal.
State media said a ceasefire was reached in the afternoon after a call by Vice President Abdrabuh Mansur Hadi for an end to the fighting and a pullout of troops and militiamen.
And the opposition warned it will not go ahead with forming a national unity government until a military commission is formed in line with a Gulf-brokered accord and the offensive on Taez halted.
Three members of a Taez family were killed in shelling blamed on government forces, while two anti-regime gunmen were shot dead during clashes with troops loyal to President Ali Abdullah Saleh, witnesses said.
The five bodies were taken to a field hospital in the Al-Rawda neighbourhood of central Taez, which is under the control of anti-Saleh protesters.
A third gunman was later killed by sniper fire in Wadi al-Qadi, while four civilians, including a woman, were wounded, witnesses said.
Saturday's casualties took the death toll from clashes and bombardments by government forces since Thursday to 31, after nine people, including a young girl, two soldiers and a colonel, were killed on Friday.
On Thursday, 16 others died, among them five soldiers and three gunmen.
The escalation of violence came hot on the heels of an order by Hadi late on Friday to cease fire and negotiate a pullout of troops and militiamen from Taez.
Gunmen backing anti-Saleh protesters control the centre of Taez and most of its streets, while government forces have taken up position on hills within the city and on its outskirts.
Witnesses said forces loyal to Saleh pounded most neighbourhoods in Taez on Saturday, while clashes raged in western parts of the city, including Al-Hasab, Beir Basha, Wadi al-Qadi and Al-Murur.
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The bloodshed sparked recriminations between the government and parliamentary opposition, which signed the hard-won accord in Riyadh that had raised hopes of an end to 10 months of violence.
Prime minister-designate Mohammed Basindawa, chosen by the opposition to head a government of national unity under the power transfer agreement, has threatened to resign unless the loyalist offensive against Taez stops.
And opposition spokesman Mohammed Qahtan accused Saleh loyalists of blocking the formation of a key commission tasked with restructuring the security forces, many branches of which are under the command of Saleh's relatives.
Hadi late on Friday ordered the governor of Taez to begin talks with the Common Forum opposition aimed at reaching a ceasefire and the withdrawal of troops and militias from the city.
Governor Hammoud al-Sufi agreed with representatives of the Common Forum on a truce starting at 02:00 pm (1100 GMT), in addition to withdrawing military units and gunmen according to mechanism to be agreed, Saba news agency said.
Hadi now holds the constitutional powers of Saleh who last month in Riyadh signed the Gulf-brokered deal under which his powers were passed on to his deputy, although he remains honorary president for three months.
Qahtan told AFP on Saturday that Hadi's directives were not enough, calling again for the formation of the military commission as stipulated in the Riyadh agreement.
The opposition will not present its nominees for a national unity government until the commission is formed, he said.
Meanwhile, local residents took action to try to stem the flow of military supplies to pro-Saleh troops from regions surrounding Taez, which lies 270 kilometres (167 miles) southwest of Sanaa.
In Al-Raheeda, 30 kilometres (19 miles) south of Taez, locals, including women and children, staged a sit-in on the main road obstructing a military convoy heading to Taez from the Anad base in Lahij, witnesses said.
Fresh protests also broke out in the capital Sanaa for Saleh to be put on trial, despite a Gulf-tailored peace deal which granted him immunity from prosecution.