Moscow: Russian President Vladimir Putin has signed a law allowing for Russia to keep its air base in Syria for another 49 years.

Russia has been providing an air cover for Syrian President Bashar Assad's offensive on the Islamic State group since 2015.

Putin signed the law late on Wednesday to ratify a deal between Russia and Syria struck in January that would let Russia use the air field just off the Mediterranean coast for free for 49 years. Two chambers of Russian parliament ratified the agreement earlier this month.

Putin did not give a timeline for Russia's operation in Syria, which he launched in 2015, and has since announced a scale down several times but Russian activities on the ground have apparently not diminished.