UPDATE 1730 GMT: An overhead view of the demolition of the regime-held “Yellow Mansion” on a hilltop on the south edge of Ariha:

Islamic Front commander Abu Issa inspects the tunnel under the Yellow Mansion:

Storming the Mansion after the blast:

UPDATE 1330 GMT: Sounds of the fighting from a vantage point above Ariha:

UPDATE 1100 GMT: While the Islamic Front attacks Ariha, other factions and Jabhat al-Nusra are trying to tie up regime forces through shelling of positions such as the “Brick Factory” and the Mastoomeh camp. Suqoor al-Sham fighters have destroyed a BMP armored vehicle with ammunition and a Shilka anti-aircraft system moving from Mastoomeh towards Ariha.

Shelling of Mastoomeh camp:

Insurgents have begun an offensive in Idlib Province in northwest Syria, seeking to take the town of Ariha.

The opposition already holds much of the province, including a line from Khan Sheikhoun from the south along a major highway through Ma’arat Numan and approaching Ariha. Last year the insurgent advance threatened to move into Ariha, just south of Idlib city, but the opposition instead consolidated the territory it had taken.

Insurgent capture of Ariha would threaten regime supply lines to Latakia Province in western Syria on the Mediterranean.

The offensive began on Thursday, but a media blackout was only lifted on Friday morning. Insurgents fired more than 500 shells and rockets, and they detonated an underground bomb which destroyed the regime-held “Yellow Mansion” on a hill on the southern edge of Ariha (see map):

The tunnel system inside the hill underneath the Yellow Mansion:

Insurgents are claiming that they have already taken regime checkpoints and destroyed a tank outside Ariha.

Islamic Front video of the firing of an “elephant” rocket: