Syrian regime troops repulsed a rebel assault on a village loyal to President Bashar al-Assad in central Homs province, killing at least 28 of the attackers, a watchdog said on Sunday.

"The number of rebels killed yesterday (Saturday) in an ambush and clashes with regime forces on the outskirts of Kafr Nan rose to 28," the Syrian Observatory for Human Rights said in a statement.

Observatory director Rami Abdel Rahman told AFP the rebels, who control Rastan and much of Houla, the towns on either side of the village of Kafr Nan, launched an assault on Saturday.

Regime troops pushed back the attack on the village, mostly inhabited by members of the Alawite community -- the offshoot branch of Shiite Islam to which Assad belongs.

Rebels also attacked a nearby regime checkpoint outside the town of Talbisseh, in the north of Homs province.

"At least six regime forces were killed but the rebels were not able to seize control of the checkpoint," the Observatory said.

Abdel Rahman said rebel fighters appeared to be "opening these battlefronts in northern Homs to relieve pressure of the town of Qusayr," where the regime launched an assault two weeks ago.

The battle for the rebel stronghold, near the border with Lebanon in southern Homs, continued on Sunday, with the Observatory reporting a continued flow of reinforcements to the regime lines.

Aid groups have expressed concern about thousands of civilians believed to be trapped in the city, with no way to escape.

Around 1,500 wounded people are also thought to be trapped inside the embattled town, a strategic prize because of its proximity to the Lebanese border and the route between Damascus and the coast.