Syrian air force strike on the border with Lebanon has killed at least 20 Syrian rebel fighters, security sources say.

Friday's attack - the latest spillover of violence into the area - hit just inside Lebanese territory in a barren area east of the town of Arsal, the sources told the Reuters news agency.

Earlier this month at least four people were killed and seven wounded in overnight air raids by Syrian forces on mountains and valleys near Arsal.

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Syrian rebel fighters have frequently crossed into Arsal, a Sunni Muslim town where residents have often been sympathetic to fighters trying to topple Syrian President Bashar al-Assad, who is from Syria's Alawite minority.

The town, which houses thousands of Syrian refugee families, has been periodically targeted with often deadly air strikes by Syria's forces in the past few months.

The attacks have killed both Lebanese and Syrian civilians.

In January rocket fire from Syria killed at least seven people in the town and wounded 15.

Lebanon, which was torn apart by its own civil war from 1975 to 1990, has been struggling to keep itself out of Syria's civil
war, which has stoked sectarian tensions across the region.

In Lebanon, groups have split along sectarian lines over the three-year conflict and the country has faced increased car bombings.

Source: Agencies