Syrian insurgents captured from government control on Thursday a town on a major highway in the west of the country after heavy fighting with pro-government militias, rebels and the Syrian Observatory for Human Rights monitoring group said.

The town of Morek is located north of Hama city on a major highway that is crucial to control of western Syria, where the Syrian army backed by allied militia and Russian air strikes has been attempting to wrest back territory from rebels.

Its capture marks a significant blow to the Russian-backed campaign that has also been supported on the ground by Iranian forces. The Russian air force began air strikes in support of President Bashar al-Assad on Sept. 30.

"This morning, it was completely liberated," Fares al-Bayoush, whose rebel group Fursan al-Haq is taking part in the fighting, told Reuters. The group is fighting under the Free Syrian Army banner. A second rebel commander also said the town had been captured.

The Observatory reported that Islamist insurgents from the Jund al-Aqsa group, backed by other fighters, seized large parts of the town.

The capture comes after months of clashes between the insurgents and fighters from the National Defence Force and other militia, said the Observatory, which tracks the conflict using sources on the ground.