More than two dozen pro-government fighters were killed in northwestern Syria overnight in a joint attack by opposition and Islamist forces, AFP reported Tuesday (July 10th).

In retaliation, the government backed by Russia pounded opposition-held areas in the coastal province of Latakia and neighbouring Idlib on Tuesday, killing four civilians, the Syrian Observatory for Human Rights said.

The surprise late Monday offensive targeted a pair of villages and observation points in the regime stronghold of Latakia, the Observatory said.

"At least 27 regime forces and allied fighters, including eight officers, were killed in fierce clashes and shelling in the village of al-Ateira," said Observatory head Rami Abdel Rahman.

"They took al-Ateira and kicked out regime forces from several observation points after killing or wounding them," he said, adding that another 40 pro-regime fighters were wounded and six opposition combatants were killed.

The death toll made the attack the bloodiest opposition assault on the area in three years, according to the Observatory.

The Observatory said the opposition fighters included local opposition fighters from Latakia as well as more hardline forces.