Syrian opposition fighters have killed 23 government soldiers in the central town of Rastan, while heavy government shelling of the town killed nine people, activists have said.
The violence came as the Arab League announced it would postpone talks aimed at uniting the Syrian opposition, after Syria's main opposition group said it would boycott the gathering that was scheduled to take place in Cairo on Wednesday.
The statement from the Arab League said the postponement had been at the request of the Syrian National Council (SNC) and the National Co-ordination Body.
Rastan, 180km north of the capital, Damascus, has slipped in and out of government control during a 14-month-old uprising in which peaceful protests have given way to sectarian-tinged violence in answer to Assad's bid to crush unrest.
Opposition activists said the soldiers were killed during clashes at dawn that followed heavy army shelling of Rastan.
"Shells and rockets have been hitting the town since 3am at a rate of one a minute. Rastan has been destroyed," a member of the opposition Free Syrian Army in Rastan, who declined to be named, told the Reuters news agency by satellite phone.
The UK-based Syrian Observatory for Human Rights said opposition fighters destroyed three armoured personnel carriers and seized two others, capturing about 15 soldiers.
Syria's Sunni Muslim majority is at the forefront of the revolt against Assad, whose minority Alawite sect is an offshoot of Shia Islam. Assad's government says it is fighting a terrorist attempt to divide Syria.
The Arab League's Secretary General, Nabil El Araby, said the move to postpone the opposition talks was based on a request from the SNC and the Syrian Co-ordination Group who requested more consultations.
El Araby said a new date has not been set, adding that the league will propose one after talks with members of the opposition.
The SNC said the group will not take part in the Arab League-sponsored talks that were scheduled to take place on Wednesday because it only received eight individual invitations.
In the statement, the SNC claimed that the meeting "turned a blind eye to the position of the SNC as the lawful representative of the Syrian People," adding that "the invitation lacked the minimum requirement for success".
Speaking to Al Jazeera before the announcement of the postponement, Radwan Ziadeh, an SNC member, said: "We had previous meetings with the secratary general of the Arab League in Cairo and Beijing, where we agreed upon three things.
"That the next meeting will be co-hosted by the SNC as being the main umbrella group of the Syrian opposition.
"That we would have a say about which people will be invited and also that we would have a role in deciding on the agenda of the talks.
"We don't have any idea about the agenda or who will be invited," Ziadeh said speaking from Rome, where the group is holding a separate meeting aimed at choosing a new leader.
Political jockeying within the SNC has prevented it from gaining full international recognition as the sole representative of the anti-Assad movement.
Executive members told Reuters they may choose a new president or restructure the council in a bid to garner broader support.
Fighting in Tripoli
Meanwhile, fighting in neighbouring Lebanon left at least eight people dead and more than 20 wounded after Alawite supporters of Assad clashed with Sunni Muslims in the city of Tripoli, medical sources said on Monday.
Fierce clashes first began on Saturday night after the arrest of a young sheikh, Shadi al-Mawlawi, and continued throughout Monday as sporadic fighting shook the northern port city.
Lebanese security forces have charged Mawlawi and five others for being part of an armed group.
In-depth coverage of escalating violence across Syria
Islamists and Salafis from different parts of Lebanon met in Tripoli's Nour Square on Monday, demanding the release of Mawlawi and the others detainees
Al Jazeera's Rula Amin, reporting form Tripoli, said the situation is "very, very tense".
"Machine guns and rocket propelled grenades were used in street fighting in the city," she said.
Mortar shells were also used for the first time on Monday evening.
"In downtown Tripoli protesters have blocked Nour Square. They want to authorities to release sheikh Mawlawi who was arrested for belonging to an armed terrorist group."
Tension between the Alawite and Sunni communities in Tripoli has been fuelled by the unrest in neighbouring Syria.
A small Alawite minority is concentrated in Tripoli, a conservative Sunni city where many residents have been enraged by the Syrian government's crackdown.