BEIRUT: Threats by Syrian armed insurgents to step up attacks on security forces, just days after their leader announced a truce that was largely ignored, have reinforced doubts over the control top officers exert over rebel fighters on the ground.

Colonel Riad al-Asaad, head of the Free Syrian Army (FSA), pledged this week to escalate operations in response to what he said was the unsatisfactory performance of Arab League monitors in halting President Bashar Assad's crackdown on protests.

The warning came just days after he said he had ordered a halt to operations against security forces while the monitors carry out their work - an order apparently disregarded by rebels who killed at least nine soldiers in three attacks.

Based across Syria's northern border in Turkey, Asaad has been described by some observers as more of a figurehead than leader of the Free Syrian Army, which says it has over 15,000 military defectors in its ranks but whose true size, membership and capabilities remain cloaked in mystery.

"I'm not sure how much control the FSA has over militants in Syria," said London-based analyst Julien Barnes-Dacey. "Most of these groups are operating on localized autonomous basis."

Attacks by the rebel army have already begun to overshadow 10 months of largely peaceful protests. Authorities have seized on them as proof that Syria faces armed Islamist fighters backed by foreign powers.

Since November rebel fighters have ambushed military convoys, attacked an airbase, seized army checkpoints and launched symbolic attacks on an intelligence center and an office of the ruling Baath Party in the heart of Damascus.

On Tuesday Asaad said the rebel army would "take a decision which will surprise the regime and the whole world" within days. "What is most likely now is we will start a huge escalation of our operations," he said.

The scale of the FSA attacks has already raised fears that the country could be slipping towards civil war.

Burhan Ghalioun, head of the main opposition Syrian National Council has urged army defectors and insurgents to limit their operations to defending peaceful protests, saying it was "fundamental for the success of our revolution to preserve its peaceful character".

That tension between the armed and political wings of the uprising is matched by the gulf between an opposition in exile rallying international support and the protesters and rebels inside Syria who act largely independently, analysts say.

"I don't think the Syrian National Council has much leverage over the Free Syrian Army, and I don't think the Free Syrian Army has much leverage itself over what is happening on the ground," said Peter Harling, an analyst with the International Crisis Group who has spent several years in Damascus.

He said the FSA was more of an umbrella for disparate fighters than a real center of command.

"People see a source of legitimacy in this (FSA) label, but what you have is groups emerging on a very local level, mostly composed of civilians, joined by defectors. But it's local dynamics rather than national."

The divisions are one reason why Western powers who rushed to support Libyan rebels seeking to overthrow Muammar Gadhafi have been more cautious with the opposition and the FSA.

Ghalioun said unless the rebels reined in their operations Syria could slip deeper into conflict "which pits a free army and an official army against each other". But in recent weeks he has faced growing criticism, even from within the SNC, for not endorsing a more forceful policy against Assad.

A spokesman for the Free Syrian Army, Major Maher al-Naimi, said Ghalioun's comments reflected his ignorance of "military basis of the (Syrian) regime", and insisted the rebels would target anyone bearing arms against civilians.

FSA statements about the size of its forces are impossible to verify, but Naimi said it had 22 brigades across the country, each led by a local leader in charge of up to six companies.

Another FSA officer called Mazen told Reuters the FSA forces were scattered around the provinces, armed with rifles and rocket propelled grenades. He said they did not have any fixed bases in the country.

FSA fighters say they are armed only with weapons they took with them when they defected, but authorities say they have seized shipments of weapons crossing into Syria from neighboring states.

The increasing violence has encouraged those protesters - a minority in the early months for the uprising - calling for foreign intervention against Assad.

"There's only a handful left in the SNC that don't want to move toward armed intervention," said one council member, who asked not to be named.

"...I'm against arming the Free Syrian Army. I see them as more harm than good, but that's it - it has become an armed revolution now."