State forces and militias loyal to President Bashar al-Assad have been accused of carrying out a "massacre" in a Syrian village.

The Syrian Observatory for Human Rights said at least 50 people, including women and children, where killed when the army stormed the coastal village of Baida.

The Observatory said the final toll was expected to exceed 100 dead.

Many of those killed appeared to be executed by gunfire or knives, it said, and other bodies were found burned.

Activist reports on the killings could not be independently verified as the Syrian government restricts access for independent media.

Hours earlier, rebels had attacked a busload of pro-Assad militiamen, known as shabbiha, killing at least six and wounding 20.

In response, government forces and shabbiha surrounded Baida and nearby Maqreb, near the city of Banias, and pummelled them with mortar fire before raiding Baida.

Assad's forces have mounted a string of attacks reaching from the capital Damascus and the central city of Homs out to the Mediterranean coast, homeland of the Alawite minority sect to which Assad himself belongs.

The two-year uprising against four decades of Assad family rule has been led by Syria's Sunni Muslim majority, and sectarian clashes and alleged massacres have become increasingly common in a conflict that has killed more than 70,000 people.

Baida was the site of one of the first sectarian clashes, when Alawite shabbiha fighters attacked Sunni street protesters in the first few months of the uprising, killing several people.

The city of Banias and surrounding villages are a largely Sunni pocket surrounded by Alawite towns.