Intense clashes have been raging since Saturday morning between the Syrian troops backed by the Lebanese Hezbollah group and the al-Qaida-linked Nusra Front near the Lebanese borders, activists reported.

The violent clashes flared between the warring camps in the barren area of Flaita in the western part of al-Qalamoun, a rugged region adjacent to the Lebanese borders between the central province of Homs and the capital Damascus, according to the Syrian Observatory for Human Rights.

Meanwhile, the pan-Arab al-Mayadeen TV denied reports that the Nusra fighters managed to storm one of Hezbollah's positions in Flaita, adding that the clashes there are still raging. No reports on losses have yet emerged.

Syrian government troops have been engaged in battles against rebel groups and extremists since 2013 in the western part of al-Qalamoun, managing to sever the rebels' main supply line from neighboring Lebanon during the battles that lasted from the winter of 2013 till the spring of 2014.

However, an array of extremist groups have for months been assembling in the eastern part of al-Qalamoun to fight both government troops and the Islamic State (IS) militants.

The battles in the eastern part of al-Qalamoun have been raging over the past two months between the IS on one side, and the Nusra Front along with the so-called Islam Army and the Eastern Loins on the other side.

The rebel-on-rebel battles in eastern al-Qalamoun are attracting more fighters to join different radical groups in that region. Reports said the battles in that region are important for the IS, which, if it wins, would besiege rival extremist groups in some pockets in the western part of al-Qalamoun and force them to pledge allegiance to it.

Hezbollah has battled alongside the government troops over the past two years, as part of its leaders' will to back the Syrian administration that has been incremental in supporting the Shiite militia against the Israeli attack on Lebanon in 2006.

The Hezbollah leader, Sheikh Hasan Nasrallah, has repeated that his fighters are fighting in Syria also to prevent the extremist groups from finding their way into Lebanon, which is not far from the raging violence next door.

Separately on Saturday, four people were killed and eight others wounded when the rebels fired multiple mortar shells into government-controlled areas in the northern province of Aleppo, according to the Observatory.

The watchdog group said the number of causalities is likely to rise, given the large number of gravely wounded people.

The Syrian troops opened fire on the rebel-held areas in the old city of Aleppo, amid ongoing clashes between the warring sides in the districts of Bani Zaid and al-Khalidiyeh, north of Aleppo, said the Observatory.

Clashes also took place between the government troops and the rebel militants in the al-Rashidien neighborhood in western Aleppo.

In Damascus, six jihadists were killed during clashes with the government troops in the Eastern al-Ghouta suburb, the Observatory said, adding that two leaders of two jihadist battalions were gunned down by unknown armed men in Eastern al-Ghouta, where intense clashes are raging, particularly in the neighborhood of Jobar.