Syrian President Bashar Assad flew to Moscow on Tuesday evening to personally thank Russia's Vladimir Putin for his military support, in a surprise visit that underlined how Russia has become a major player in the Middle East.

It was Assad's first foreign trip since the outbreak of the Syrian crisis in 2011, and came three weeks after Russia launched a campaign of airstrikes against Islamist militants in Syria that has also bolstered Assad's forces.

The Kremlin kept the visit quiet until Wednesday morning, broadcasting a meeting between the two men in the Kremlin and releasing a transcript of an exchange they had. It did not say whether the Syrian leader was still in Moscow or had returned home.