President Vladimir Putin has been granted permission from the upper house of Russia's parliament to carry out air strikes in Syria following a request from the Kremlin.

Kremlin spokesman Dmitry Peskov said Russia's main military goal was to combat terrorism — assumed to be in reference to Islamic State militants (IS) — and support the forces of president Bashar al-Assad.

"The main objective is the fight against terrorism and supporting the legitimate authorities in Syria in the fight against terrorism and extremism," he said.

Early on Wednesday, Mr Putin submitted a proposal to the Federation Council to deploy "a contingent of troops" abroad, the Kremlin said in a statement.

Later in the day in televised remarks, the head of the presidential administration Sergei Ivanov said parliament had backed military action by 162 votes to zero.

"We're talking specifically about Syria and we are not talking about achieving foreign policy goals or about satisfying our ambitions ... but exclusively about the national interests of the Russian Federation," he said.

Mr Ivanov added Syria had asked Russia for military help, and the use of Russia's military only related to the use of the air force, not boots on the ground.

The Syrian presidency confirmed Damascus made a request to Moscow, and Mr Assad had written to his Russian counterpart regarding the matter.

"Any increase in Russian military support to Syria happened and is happening as a result of a request from the Syrian state," Mr Assad's media office said in a statement.

Mr Peskov said the decision meant Russia would be practically the only country in Syria to be conducting operations "on a legitimate basis" and at the request of "the legitimate president of Syria".

The Russian president requested similar permission from the Federation Council to deploy military forces abroad ahead of the annexation of Crimea in March 2014.

Russia has been a staunch ally of the Syrian regime throughout the country's civil war. ( Reuters: Khalil Ashawi )

The Pentagon has in recent weeks said Russia sent bombers, fighter jets, at least 500 troops and a slew of other military hardware to north-western Syria in what many fear is an attempt to keep the war-torn country's president in power.

A Russian official told news agency Reuters, Moscow had sent military experts to the recently established centre in Baghdad which coordinated air strikes and ground troops in Syria against IS.

A US-led coalition is already fighting the group in both Syria and Iraq with air strikes, but it does not coordinate with Syria's government.

On Monday, Mr Putin called for a broad UN-backed coalition to fight IS as he addressed the UN General Assembly for the first time in a decade.

Analysts said Mr Putin needed to get parliament's backing to ensure that any military operation was legal under the terms of the Russian constitution.

"If there will be a united coalition, which I doubt, or in the end two coalitions — one American and one Russian — they will have to coordinate their actions," Ivan Konovalov, a military expert, told Reuters.

"For Russian forces to operate there legitimately ... a law was needed."

Russia's Syria build-up is Moscow's first military engagement in a distant theatre of war since the Soviet intervention in Afghanistan in 1979.

AFP/Reuters