The military campaign by Russia, Syria and its allies is vital to save the Middle East from destruction, Syrian President Bashar al-Assad said, a day after Moscow said it would step up air strikes against Islamic State targets across Syria.

A year-long air campaign by Western and Arab air forces in Syria and Iraq had been counterproductive, Assad said, helping terrorism spread and win new recruits, but a coalition of Syria, Russia, Iran and Iraq could achieve real results.

"It must succeed otherwise we face the destruction of the entire region, not only one or two states," he said in an interview with Iranian television broadcast on Sunday.

Assad was speaking days after Russian jets based in western Syria launched air strikes against targets Moscow has identified as Islamic State bases, but which Assad's opponents say disproportionately hit rival, foreign-backed insurgents.

The United States, France and Britain say the Russian air strikes are aimed at propping up Assad after recent rebel advances. "They are backing the butcher Assad, which is a terrible mistake, for them and the world," British Prime Minister David Cameron said.

Russia said on Sunday its planes flew 20 sorties in Syria and struck 10 Islamic State targets in the previous 24 hours, including a training camp and a suicide-belt factory.

"We have managed to disrupt their control system, the terrorist organisation's supply lines, and also caused significant damage to the infrastructure used to prepare acts of terror," Russia's defense ministry said.

Residents in the Syria province of Homs reported air strikes on Sunday they believed were carried out by Russian jets, in an area controlled by factions fighting under the umbrella of the rebel Free Syrian Army, not Islamic State.

"So far there are seven or six raids in the town," said Abdul Ghafar al Dweik, a volunteer rescue worker in the town of Talbiseh, adding that the air strikes were different to previous attacks by Syrian warplanes.

"With the Syrian planes, we would get a warning but now all of a sudden we see it over our heads," he said.

At least five bodies were recovered in the western part of Talbiseh, he said. Ambulances rushed wounded people to hospital.

Al Qaeda-linked Nusra Front said in a statement that fighters in the region around Talbiseh - a pocket of insurgent-controlled land - were forming a joint military "operations room" to coordinate operations.

A separate statement in the name of dozens of Free Syrian Army officers said they would take part in the unified command "to confront the Russian and Iranian occupation".

Elsewhere in Syria, Russian jets struck near Raqqa, the Syrian stronghold of Islamic State fighters, a Syrian military source said, as well as the western towns of Maarat al-Numaan and Jisr al-Shughour, where rival insurgents are more prominent.

"TERRORISM HAS SPREAD"

Assad said air strikes by Syrian jets, now joined by Russia, had been far more significant than anything achieved by the year-long air campaign by the United States and its Western and Arab allies, who Assad accused of hypocrisy because of their support for insurgents fighting in Syria.

"Countries which support terrorism cannot battle terrorism," he said. "That's the truth of the coalition that we see... That's why after a year and several months we see no results."

"We see the opposite... terrorism has spread geographically and won more volunteers and recruits".

Syria's conflict grew out of protests against Assad's rule in early 2011, which were put down by force and then turned violent, drawing in regional opponents and supporters of the Syrian leader.

Efforts to find a political solution to the civil war have so far proven fruitless, with most rebel fighters demanding Assad's departure as a precondition for talks. Western states also say Assad must step aside, though most have softened their stance to say he could play some role in a transition period.

"In regard to their recent statements about a transitional period and other issues, I say clearly that it's not up to any foreign official to decide Syria's future," Assad said.

"The future political system, and which individuals govern Syria, this is a decision for the Syrian people. That's why these statements don't concern us."