DAMASCUS  - Syrian security forces carried out a spate of raids in Damascus on Tuesday after a deadly bombing hit the capital and UN chief Ban Ki-Moon warned the search for peace was at a "pivotal moment ."
State television said the late Monday blast hit a restaurant in the Qaboon neighbourhood of the capital, with the Britain-based Syrian Observatory for Human Rights saying five people were killed.
In all, at least 59 people were killed nationwide on Monday, including 31 loyalist troops who died in clashes with rebel fighters, the Observatory said.
The bloodshed raged despite the deployment of a UN military observer mission to oversee a promised ceasefire that has been breached daily since it went into force on April 12.
Gunfire erupted as a team of UN observers visited the town of Busayra in Deir Ezzor province in the northeast, activists reached by Skype told AFP.
"Unconfirmed reports indicate there are two dead and several wounded," one activist said. The Observatory said dozens of people were arrested in the pre-dawn raids in several suburbs of the capital, including Douma, Harasta and Barzen.
It said powerful blasts were heard overnight in a number of provincial cities, including central Hama, northern Aleppo and the coastal cities of Banias and Latakia.
The watchdog said there were also fierce clashes between regime forces and rebels in the town of Kfar Roma in Idlib province in the northwest, with four soliders having been killed in fighting.
And the Observatory said there were reports that regime helicopter gunships had opened fire in certain parts of Idlib, wounding an undetermined number of people.
Demonstrations broke out at dawn in several neighbourhoods of Aleppo, the country's second city and commercial hub which until recently had been largely spared the unrest shaking the country since March last year.
One person was killed by gunfire in Nouaymeh, a town in the southern province of Daraa, the Observatory said.
The UN chief issued a new warning on the dangers of all-out civil war as the 14-month uprising against President Bashar al-Assad's regime has turned into an armed rebellion.
"The secretary general said we were at a pivotal moment in the search for a peaceful settlement to the crisis and that he remained extremely troubled about the risk of an all-out civil war," a spokesman for Ban said at a NATO summit in Chicago on Monday.
NATO states have come under criticism for backing the air war in Libya last year that helped insurgents defeat Moamer Kadhafi's forces but ruling out military intervention in Syria, where badly outgunned rebels have been hammered by heavily-armed regime troops.

In neighbouring Lebanon, protesters blocked roads in the northern Akkar region for a third day on Tuesday, a security official said, amid mounting tension over the conflict in Syria.
The road closures were linked to the weekend killings of two clerics at an army checkpoint in Akkar, a mainly Sunni region whose inhabitants are hostile to Assad's regime.
The killings ignited street battles in the capital Beirut that left two people dead and 18 wounded.
Separately, Syrian rebels kidnapped 13 Lebanese Shiite Muslims in Aleppo province as they were headed home by bus from a pilgrimage in Iran, Lebanon's national news agency reported.
Reports of the kidnappings prompted families of those abducted to gather in Beirut's mainly Shiite southern suburbs to demand their release.
Amnesty International called on the Lebanese authorities to launch an independent investigation into the deaths of the two clerics on Sunday.
"It's vital the probe into these killings is carried out by an independent body," said Amnesty's deputy director for the Middle East and North Africa, Ann Harrison.
A Lebanese judicial official said 21 soldiers, including three officers, were being questioned by military police in relation to the clerics' deaths.
A military judge meanwhile ordered the release on bail of an Islamist whose arrest had been another source of friction between pro- and anti-Syrian groups, a judicial official said.
Shadi al-Mawlawi's May 12 arrest on charges of belonging to a terrorist organisation sparked sectarian clashes in the northern port city of Tripoli that left 10 people dead.
His supporters say he was targeted because he was helping Syrian refugees fleeing the unrest in their country.
The unrest in Lebanon has highlighted deep divisions in the country over Syria.
The opposition led by former premier Saad Hariri backs the revolt against Assad, while the ruling coalition, in which the powerful Shiite movement Hezbollah plays a key role, supports the Damascus regime.
Hezbollah's Al-Manar television said the head of the movement, Hassan Nasrallah, would speak about the kidnappings in a televised address at 7:30 pm (1630 GMT).