Vladimir Putin has vowed Russia’s military will “immediately destroy” any target threatening them in Syria, representing a strong warning to Turkey following its shooting down of a Russian warplane at the Syrian border. Putin said the military should respond with full force to any “further provocations”, adding that additional aircraft and air defence weapons have been sent to the Russian base near Latakia.

“I order you to act in the toughest way,” the Russian president said. “Any targets threatening the Russian groups of forces or our land infrastructure should be immediately destroyed.” The downing of the Russian bomber by a Turkish fighter jet, the first time a Nato member shot down a Russian plane in more than half a century, has badly strained relations between Moscow and Ankara.

Putin said Russian military action in Syria was essential to protect Russia from extremists based there, adding that fending off that threat is the main goal of the air campaign he launched on 30 September. The campaign took advantage of western disarray and galvanised efforts to end the four-and-a-half-year war.

Western countries say Russian air attacks have targeted rebels fighting President Bashar al-Assad far more than Isis, reinforcing the impression that Moscow’s main goal is to bolster its long-standing ally in Damascus.

The US and Britain have meanwhile welcomed agreement by Syrian opposition groups to hold talks with Assad in the new year. But the Syrians are still insisting he stands down at once – in the face of strong resistance from Russia and Iran, the president’s closest allies.

Ahrar al-Sham, one of the biggest armed Islamist groups, which is backed by Turkey, walked out before the Riyadh meeting ended, though it did sign the statement. It objected to the role given to the Damascus-based group, the National Coordination Body for Democratic Change, which is tolerated by Assad.