Syrian insurgents captured a town on a major highway in the west of the country on Thursday and fought fierce battles with pro-government militias around it, 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.

Warplanes believed to be Russian were bombing Morek and its surroundings following the capture, the Observatory said.

"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 seized.

Bayoush said the town was strategically important. "It was a center for the gathering of regime forces and a point of departure for its operations," he said.

Government forces fought for months to take control of the town in October 2014 and lost many fighters, the head of the Observatory Rami Abdulrahman said. He said fighting was continuing inside parts of the town.

"They worked hard to retake it last year and now they lost it in a few hours," he said, adding that insurgents entered the town easily, through government checkpoints, and seized large parts in the west.

Syrian state media made no immediate mention of Morek's capture.

'HAMA IS AFLAME'

Dozens of pro-government fighters were killed and insurgents seized vehicles, heavy machine guns and 10 tanks, said a media activist in the rural region of Hama province where Morek is located.

"The whole countryside of Hama is aflame... The offensive started two days ago, launched by Jund al-Aqsa," the activist, who asked to remain anonymous, said via an internet messaging service.

"They started the offensive with heavy mortar shelling as preparation before storming. This was followed by fighters who broke into the town, then heavy machine gun fire and shelling," he said, adding the capture took around eight hours in total.

The Observatory reported that Islamist insurgents from the Jund al-Aqsa group, backed by other fighters, took the town overnight after firing hundreds of shells and rockets.

Overall the Syrian army and allied militia had not made significant progress after a month of Russian strikes, he said. "We cannot say the regime is going forward, no way," said Abdulrahman, who tracks the conflict using sources on the ground.

A Syrian military source had previously told Reuters the government operations were going according to plan.

Russia has recently stepped up efforts to broker a peace deal between Syrian government officials and members of the country's splintered opposition.

Deputy Foreign Minister Mikhail Bogdanov said the Kremlin would invite representatives of both sides to meet in Moscow next week, and a Russian news agency reported that an FSA delegation has agreed to meet Russian officials in Abu Dhabi late next week.

But representatives of FSA-affiliated groups that receive backing from foreign states opposed to Assad dismissed the report. Bayoush said the Russians had been meeting Syrians who falsely claimed to be FSA.

Bashar al Zoubi, a prominent rebel figure, said there was no sign that the Russians wanted an 'honest solution' to the war, and therefore there was no contact with them.

The Syrian opposition National Coalition representative to the Gulf Arab states, Adib Shishakly, denied news of the FSA-Russia meeting, saying it was untrue.