A brigadier general and about 20 soldiers defected from the Syrian army in two separate incidents on Saturday, activists said, in another sign that the strength of President Bashar al-Assad's armed forces is diminishing.

Brigadier General Mohammed Khalouf appeared dressed in a camouflage military uniform in a video on Al Arabiya news channel and said he had planned his escape with the opposition movement for some time.

"It is not possible for anyone to accept any of the ideas of this regime unless they have achieved special interests," he said in the video.

There was no comment about the defection on Syrian state news outlets.

Defection of high-ranking military and political figures has slowed in past months.

But a study by the International Institute for Strategic Studies (IISS) published this week estimated that Assad's forces, thought to be more than 300,000-strong at the start of the uprising two years ago, were now at a much lower effective strength and were likely to diminish further.

The IISS said that perhaps 50,000 of the Syrian army's elite troops could be depended on for loyalty. Most of them were likely to be from Assad's minority Alawite sect, which has dominated the country for more than four decades.

Many deserters report that their units were held inside bases to prevent their escape.

Syria's civil war began as a popular street movement but has evolved into an increasingly sectarian conflict. The opposition has been mostly led by the Sunni Muslim population, with Alawites and other minorities mostly throwing their weight behind Assad.

In central Syria, around 20 soldiers fled their posts for embattled rebel territory near the ancient desert city of Palmyra, according to the Syrian Observatory for Human Rights.

The British-based group, which has a network of activists across Syria, said the soldiers fled to farmlands near the city, where there has been shelling and gun battles for two days.

Fighting has now spread across most of the country, except for a stronghold on the Mediterranean coast which is home to a large Alawite population.

With increasing violence has come a rising use of cluster munitions, the Human Rights Watch reported Saturday, saying it had identified at least 119 locations across Syria where the bombs had been used in the past six months. It said cluster bomb attacks were causing a mounting civilian death toll in a conflict that has already killed more than 70,000 people.

"Syria is expanding its relentless use of cluster munitions, a banned weapon, and civilians are paying the price with their lives and limbs," said Steve Goose of Human Rights Watch.

"The initial toll is only the beginning because cluster munitions often leave unexploded bomblets that kill and maim long afterward," he added.-Reuters