Just days after a Russian civilian plane was suspected to have been shot down by a radical Islamist group, Moscow announced that after evaluating the threat it has deployed the S-300 anti-aircraft missile system around the Latakia airbase in Syria to counter any threat.

The Russian defence ministry has said the deployment of the anti-aircraft system will not only secure its airbase in Syria, but also deter any attempt to hijack its warplanes.

Russia's Aerospace Forces Commander-in-Chief Colonel General Viktor Bondarev told Russian dailies on Thursday the country was taking all measures to secure its assets in Syria.

"We have studied all the possible threats," said Bondarev, adding that it has also sent in missile systems besides "fighter jets, attack aircraft, bomber aircraft, helicopters," Tass reported.

Despite earlier reports dismissing the claim that the Islamic State (or Isis) was not behind the Russian plane crash, multiple sources now suggest that Isis might have planted a bomb on the aircraft.

Several US officials have also told CNN a bomb was likely planted on the plane by Isis.

British Foreign Minister Philip Hammond also toed the same line when he said his government strongly believes an explosive device aboard the plane caused the crash. The same view is also held by Middle Eastern intelligence officials.

The S-300 Russian long-range surface-to-air missile systems were developed to defend against aircraft and cruise missiles. They can also intercept ballistic missiles.