The risk of civil war looms large over Syria as army defectors increasingly take aim at regime forces and diplomacy fails to resolve the escalating crisis, experts say.

"We are moving down that track and the longer the international community and the Arab League delay (action), the sooner we will be there," said Salman Shaikh, head of the Brookings Doha Center.

"The continuing intransigence of countries like Russia will only lead us to a situation whereby no one will want to talk politics and (the Syrians) will start to fight each other," Shaikh told AFP.

The eight-month revolt in Syria has turned increasingly violent, with the Free Syrian Army, made up of army defectors, mounting a daring attack this week against a military intelligence base near the capital and the opposition becoming more militarised.

The international community, notably Washington, has expressed concern about the use of violence by the opposition, warning it plays into the hands of the regime.

The United Nations is also fearful of civil strife and Syria's allies in Moscow on Thursday said the previous day's attack by renegade troops looked like the start of a civil war.

But analysts say that while the risk of such a conflict exists, they did not believe it was imminent.

"The risk for generalised civil war is real though we are not there yet," said Marwa Daoudy, lecturer at Oxford University's department of politics and international relations.

And a former French diplomat with long experience in Syria said he believes those leading the revolt against the regime of President Bashar al-Assad were still keen to avoid violence.

The diplomat, who requested anonymity, warned however that the regime, feeling cornered on all sides, was now pushing for the conflict to turn sectarian.

The Syrian government is dominated by the minority Alawite sect, an offshoot of Shiite Islam, while the majority of the population is Sunni Muslim.

"The regime has done so many horrible things that at some point there is the risk of explosion," the former French diplomat said.

But experts believe that in the event of civil war, the conflict would not necessarily be sectarian but would pit renegade soldiers and the opposition against a regime bent on holding on to power.

"Civil war would not necessarily imply strife between Alawites and Sunnis despite the regime's attempts to scare the Alawite community with potential future retaliation on the part of the Sunnis," Daoudy said.

The political opposition, at least for now, has steered clear of taking up arms and pushed for the revolt to remain peaceful.

"We are at a turning point," Burhan Ghalioun, who heads the Syrian National Council, the largest and most representative opposition group to have emerged since mid-March when the revolt erupted, said on Thursday.

"One path can lead us to freedom and dignity, the other toward a civil war that the regime keeps pushing for in order to undercut the revolution," Ghalioun, a professor of political sociology in France, added in a statement.

He said sectarian-based kidnappings and killings were already taking place in several parts of Syria, notably in the central city of Homs and in Daraa, to the south.

But experts say that such incidents for now are isolated and it was up to the opposition to stick to the largely peaceful nature of the revolt, despite a crackdown that has left more than 3,500 people dead, according to the UN.

"It is remarkable to what extent the protesters have resisted the efforts of the regime to sow sectarian strife in the country," said Shaikh.

"Everything that I have heard from the opposition (indicates) a desire, even in the transitional phase, to make sure all minorities" are included in any future government, he added.

"They don't want an Iraq-like scenario where the (minority) Sunnis woke up one day and found out they had lost everything."