Deadly car bombings and artillery fire on Friday shattered a fragile truce between the warring parties in Syria just hours after it had begun on the first day of the Muslim Eid al-Adha holiday.
State television blamed "terrorists," the regime term for rebels, for a car bomb attack in Damascus that killed at least five people and wounded dozens, and a rights watchdog reported another deadly bombing farther south in Daraa.
Rebels accused regime forces of opening up with artillery in the embattled north, where the Syrian Observatory for Human Rights said fighting erupted near the key army base of Wadi Deif.
The army said it was responding to attacks by armed rebels that violated the truce agreed to mark Eid al-Adha, one of the most sacred holidays in Islam, which started at dawn.
UN and Arab League envoy Lakhdar Brahimi had brokered the ceasefire in the hope that if successful, it could lead to a longer cessation of violence.
President Bashar al-Assad's forces and main rebel group the Free Syrian Army (FSA) had both agreed to a call by Brahimi to lay down their arms for the four-day Eid, but both also reserved the right to respond to attacks.
"Armed terrorist groups attacked military positions, thereby clearly violating the halt to military operations agreed by the army command," the military said in a statement read on state television.
"Our valiant armed forces are responding to these violations and pursuing these groups," it added.
An FSA commander in the northern city of Aleppo accused the regime of breaking the pledge to stop firing.
"The regime does not respect the ceasefire, it is not shooting and there are no clashes but it has started shelling... What ceasefire? We can't trust the regime," said Abd al-Jaber al-Akaidi.
"The regime is perfidious, a cheater and a liar."
The rebel jihadist group Al-Nosra Front, which has claimed responsibility for deadly car bombings in the past, had refused to sign up to the ceasefire.
As the day progressed it became clear there had been little let-up in the violence.
The Britain-based Observatory reported car bombings in Damascus and in Daraa, cradle of the anti-regime revolt that has become a fully fledged uprising since it first erupted in mid-March last year.
The watchdog said the a car bomb blew up outside the Omar bin Khattab mosque of the Daf Shawk district in southern Damascus, killing five people and wounding more than 30, adding that children were among the casualties.
State television reported at least five people killed and 32 wounded in the "terrorist" act.
A security source told AFP the bombing had targeted residential buildings for police officers and their families, and that children were playing in the area when the blast occurred.
In Daraa, three soldiers were killed and eight wounded when a car bomb exploded near a military checkpoint and the railway station, the Observatory said. Eight troops were wounded, most of them critically.
-- Assad joins Eid prayers --
The Observatory said the truce had "collapsed" in several regions and gave a death toll of 61 on Friday, a day after 135 were reported killed, adding to an estimated death toll of 35,000 people over 19 months of conflict.
Observatory director Rami Abdel Rahman reported fighting in various parts of Syria, including in and around Damascus, in second city Aleppo, in the central city of Homs and near the Wadi Deif base in the northwest.
At least 10 soldiers and four rebels were killed at Wadi Deif, the watchdog said.
The Observatory relies on a countrywide network of activists and medics in civilian and military hospitals, and says its tolls take into account civilian, military, and rebel casualties.
In Aleppo, scene of fierce fighting since mid-July, there was a brief morning respite and children playing in the streets of some neighbourhoods, an AFP reporter said.
Some families also ventured out to check on their homes on the front line, taking advantage of the lull, the reporter said.
Residents reported clashes at mid-day after rebels tried to overrun a checkpoint near the Mohasab army base in the northeast Seryan district, and in the Sheikh Maqsud area between Kurdish militias and rebels.
Shams, a mother in the city's army-controlled Sabil district, said the ceasefire "is only a political phrase and not a reality on the ground."
Brahimi had hoped a temporary truce could lead to a more permanent ceasefire during which he could push for a political solution and bring aid to the most stricken regions.
After clashes late Thursday, the ceasefire began as morning prayers marked Eid al-Adha, the Feast of Sacrifice capping the end of the annual hajj pilgrimage to Mecca.State television showed Assad joining Eid prayers at a Damascus mosque, smiling and chatting with worshippers.
The truce was also tested as security forces opened fire to disperse anti-regime protests after prayers at Inkhel in Daraa, wounding three people, the Observatory said.
General Mustafa al-Sheikh of the FSA said the rebels considered the protest crackdown a violation of the ceasefire, but they were not planning to respond.