Russian military jets are seen at Hmeymim air base in Syria, June 18, 2016.[Photo/Agencies]

MOSCOW -- Russian President Vladimir Putin has signed into law a protocol to an agreement with Syria to deploy the Russian air forces at a Syrian military base, the Russian government said Wednesday.

The document was posted on the Russian government's legal information portal.

The law ratifies the agreement signed by Russia and Syria which allows the Russian air group to use Syria's Hmeymim airbase free of charge for 49 years with possible extension for another 25-year period.

The protocol to the 2015 Russian-Syrian agreement "aimed at establishing the international legal framework governing the conditions for the location of the Russian air force group" was signed in Damascus on Jan. 18, 2017.

Prior to being signed into law by Putin, the protocol was ratified by both chambers of the Russian parliament.

The Russian air group was deployed at Hmeymim from the end of September 2015 to help Syria fight the Islamic State (IS) and other terrorist groups at the request of Syrian President Bashar al-Assad.