Syrian President Bashar al-Assad has said Donald Trump could be a "natural ally" if he fulfils his pledge to fight "terrorists".

Speaking for the first time on Mr Trump's unexpected election victory, Mr Assad said he was unsure the US President-elect would be able to keep his word and step up the fight against jihadists.

"If ... he is going to fight the terrorists, of course we are going to be ally, natural ally in that regard with the Russian, with the Iranian, with many other countries," Mr Assad told Portugal's RTP state television.

On Friday, Mr Trump indicated that he will focus on fighting Islamic State in Syria rather than attempting to oust Mr Assad's regime.

He told the Wall Street Journal he had "an opposite view of many people regarding Syria", adding: "We're backing rebels against Syria and we have no idea who these people are."

Asked about Mr Trump's pledge to crack down on IS, Mr Assad said: "I would say this is promising, but can he deliver?

"Can he go in that regard? What about the countervailing forces within the administration, the mainstream media that were against him? How can he deal with it?

"That's why for us it's still dubious whether he can do or live up to his promises or not. That's why we are very cautious in judging him, especially as he wasn't in a political position before."

Mr Assad added that the US "think that they are the police of the world".

He said: "They think they are the judge of the world. They're not."

His comments come after a telephone conversation between Mr Trump and Vladimir Putin, during which the pair reportedly agreed to work together to tackle international terrorism and extremism.

Meanwhile, Russia has launched a major air offensive in Syria as part of a joint operation with Mr Assad's regime.

Targets in Idlib and Homs were hit by jets which took off from the Admiral Kuznetsov aircraft carrier, while the Syrian military attacked rebel groups inside east Aleppo.

Russian defence minister Sergei Shoigu said the main targets included IS and al Nusra ammunition depots, as well as weapons factories.