Syrian regime forces were close to capturing a rebel stronghold in the southern province of Daraa on Monday, backed by Russian air strikes, a monitor and state media said.

"Army units are continuing to progress on several axes in Sheikh Miskeen," state news agency SANA said.

The Syrian Observatory for Human Rights, a Britain-based monitor, reported heavy fighting and several dozen Russian air strikes on the town.

"Regime forces now control around 70 percent of Sheikh Miskeen," Observatory chief Rami Abdel Rahman said.

The group did not have an immediate casualty toll for in the fighting.

The town is strategically important because of its location on a crossroads between Damascus to the north and the city of Sweida to the east, both of which are under government control.

It also lies about 12 kilometres (seven miles) from the rebel stronghold of Nawa, another key target for regime forces.

A security source told AFP the town was a "launching pad" for rebel operations, and one of the opposition's "centres of gravity for the whole of Daraa province".

He said seizing control of the town would sever a key rebel supply route to areas under opposition control around Damascus.

Last month, government troops captured the Brigade 82 base outside the town, and they have since been pushing to capture Sheikh Miskeen.

Most of Daraa province is controlled by opposition forces, though the government holds parts of the provincial capital and a few villages in the northwest.

Syria's loyalist army has been on the offensive since staunch government ally Russia began an aerial campaign in support of regime forces on September 30.

Since then, the regime has recaptured several key rebel towns in coastal Latakia province, as well as advancing in the northern province of Aleppo and in Daraa.

Russia denies report of new military base in north Syria
Moscow (AFP) Jan 25, 2016 - Russia's defence ministry on Monday denied reports that it is building a new military base in Syria, where it has pursued a bombing campaign for the past four months.

"There are no new airbases or additional aerodromes for Russian warplanes in the Syrian Arab Republic, and no plans to create any," defence ministry spokesman Igor Konashenkov told Russian news agencies.

Western media outlets have reported that both Moscow and Washington are establishing covert military bases near Syria's border with Turkey.

The reports followed a claim by Turkish President Recep Tayyip Erdogan that up to 200 Russian soldiers were working on a runway at an airbase in the northeastern Syrian city of Qamishli on the Turkish border.

Britain-based monitor the Syrian Observatory for Human Rights alleged that Russia had sent a number of engineers to the border town to strengthen the runway and increase the capacity of the airport there.

But Konashenkov on Monday said only "absolute morons" could seriously discuss alleged Russian activity in Qamishli, saying the reports were an attempt to "cover up the build-up of a large Turkish military force" at the Syrian border.

Reports of Russia's alleged move into Qamishli came as Ankara and Moscow are embroiled in their worst diplomatic crisis in years after Turkey shot down a Russian war plane on November 24.

Russia officially operates a naval facility in the Syrian port city of Tartus, as well as an airbase on the outskirts of the coastal city of Latakia.

Moscow launched a bombing campaign in war-torn Syria at the request of long-time ally President Bashar al-Assad on September 30.

The defence ministry said Monday that Russian jets had bombed 484 "terrorist infrastructure" targets in 169 combat sorties between January 22 and January 24.

The latest strikes, according to the Russian military, had helped Syrian armed forces in the Latakia region "liberate more than 92 square kilometres of territory and 28 communities from terrorists" in the past 24 hours.

The Russian defence ministry says its strikes are targeting the Islamic State group and other extremist organisations, but the West has accused Moscow of targeting more moderate groups that oppose the Assad regime.