• Video report by ITV News Security Editor Rohit Kachroo

The "murderously efficient" Islamic State (IS) is currently plotting violent attacks against the UK from Syria despite being under military pressure, the head of MI6 has warned.

Alex Younger said the scale of the terror threat is "unprecedented" as he highlighted how intelligence and security services have disrupted 12 terrorist plots in the country over the last three years.

The spy chief attacked Russia for backing Bashar Assad's "discredited" Syrian regime, warning that defining opponents as terrorists alienated people who must be brought onside if extremists are to be defeated.

"The plight of the Syrians continues to worsen. I cannot say with any certainty what the next year will bring," said Mr Younger.

"But what I do know is this - we cannot be safe from the threats that emanate from that land unless the civil war is brought to an end."

In his first public speech since taking up the post of "C", Mr Younger also warned that "hybrid warfare", which includes cyber attacks and subverting democracy as well as more traditional methods of attack, was becoming an "increasingly dangerous phenomenon".

He added: "The risks at stake are profound and represent a fundamental threat to our sovereignty. They should be a concern to all those who share democratic values."

IS, also known as Daesh, exploited Syria's civil war to bolster its stronghold in the region and wage a war on the West.

Last month it was revealed that coalition forces fighting militants in Syria and Iraq had discovered more than 10,000 documents detailing thousands of plots to attack Europe.

Mr Younger said the service must "take the fight to the enemy" by penetrating terror organisations.

The scale of the threat is unprecedented. The UK intelligence and security services have disrupted 12 terrorist plots in the UK since June 2013.

Alex Younger, MI6