A Syrian army officer says the battle against the Islamic State group in an area along the border with Lebanon will end within hours.

The colonel's comments to the Lebanon-based Al-Mayadeen TV on Thursday came as Lebanese artillery and aircraft pounded IS positions on the other side of the border as part of Lebanon's own offensive against the extremists.

The Lebanese army command said the fourth phase of the offensive that began on Saturday should eventually evict all IS fighters from the border region.

The Syrian army and its ally, the Lebanese Hezbollah group, launched an operation simultaneously with the Lebanese to clear IS from the Syrian side of the border in the western Qalamoun mountain range. Hezbollah has been fighting in Syria alongside President Bashar Assad's forces since 2013.