In an interview with Britain's Sunday Telegraph newspaper, Syria's President Bashar Al-Assad warned of "another Afghanistan" if foreign forces intervened in his country as they had with the Libyan uprising that toppled Muammar Gaddafi.
"Syria is the hub now in this region," the paper quoted Al-Assad as telling one of its journalists in Damascus.
"It is the fault line, and if you play with the ground you will cause an earthquake -- do you want to see another Afghanistan, or tens of Afghanistans?
"Any problem in Syria will burn the whole region. If the plan is to divide Syria, that is to divide the whole region."
His warning came as 20 Syrian soldiers were killed on Saturday and 53 wounded in clashes with presumed army deserters in Homs, while 10 security agents and a deserter were killed in a bus ambush, activists said.
The violence, in which loyalist and anti-regime casualties predominated in what is the worst surge of killing in six months, came as 12 civilians died and several were wounded by government gunfire.
In the area of Homs, at least 12 civilians died from fire by snipers and machineguns, while an undetermined number of others were killed in their homes by security forces, the Syrian Observatory for Human Rights said.
UN chief Ban Ki-moon urged Syria to "immediately" end attacks on civilians after dozens died in a fierce crackdown on dissent by Syria's security forces on Friday, which was also condemned by the Arab League.
In the attack on the bus, the Observatory said it had been transporting security agents between the villages of Al-Habit and Kafrnabuda in Idlib province, close to the Turkish border.
It had been ambushed "by armed men, probably deserters", it said.
The clash left 10 security agents and a deserter dead, said the Britain-based watchdog, which earlier reported 17 soldiers killed late Friday in the central city of Homs.
Suspected deserters had attacked two checkpoints.
Homs and Hama provinces have been at the forefront of anti-government protests that have been brutally put down by the security forces. According to the UN, the crackdown has claimed more than 3,000 lives, mostly civilians.
Ban's appeal came after activists said 36 people were killed on Friday by security forces during mass protests calling for the imposition of a Libya-style no-fly zone on Syria.
Ban "appeals for military operations against civilians to stop at once," said his spokesman Martin Nesirky.
"The violence is unacceptable and must stop immediately," he added. "The calls of the Syrian people for change must be answered with far-reaching reforms, not repression and violence."
Friday's violence prompted fresh condemnation from the foreign ministers of the 22-strong Arab League, which has been trying to broker an end to the unrest that has rocked Syria since anti-regime protests erupted in March.
An Arab League task force met Assad on Wednesday in Damascus and was due to hold talks Sunday in Qatar with top Syrian officials to try to reach "serious results and an exit to the Syrian crisis," it said.
But Syria's foreign ministry accused the Arab committee of stoking dissent, having been influenced by "lies spread by television channels".
It said Foreign Minister Walid Muallem would "inform the committee tomorrow of the true situation in Syria," the state-run news agency SANA reported.
The latest violence was the deadliest in nearly six months to occur on a Friday, the day worshippers emerging from weekly prayers at mosques defy the security forces and swarm the streets to rally against the regime.
The bloodiest Friday was on April 22, when the death toll reached 72.