Russian President Vladimir Putin has signed a law ratifying a deal with the Syrian government to allow Russia to keep its airbase in Syria for almost half a century.

The original deal, signed in Damascus in January, set out the terms under which Russia can use its Hmeymim air base in Latakia Province, which it has used to carry out air strikes against forces opposing President Bashar al-Assad.

Mr Putin approved the agreement after the two chambers of the Russian parliament backed it earlier this month, according to the government's official information portal.

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The document says Russian forces will be deployed at the Hmeymim base for 49 years with the option of extending that arrangement for 25-year periods.

The base has been at the heart of Moscow's military foray since it intervened in the conflict in September 2015, helping turn the tide in favour of Assad, one of Russia's closest Middle East allies.

Syrians make fuel from plastic waste Show all 8 1 /8 Syrians make fuel from plastic waste Syrians make fuel from plastic waste Sifting through plastic: the workshop uses plastic from bottles and other waste materials to produce liquid and gas fuels. The liquid is refined into gasoline, diesel and benzene fuels, which in turn are sold for domestic and commercial use Reuters Syrians make fuel from plastic waste Khodor, 20, at the workshop in the rebel-held and besieged neighbourhood of Douma, Damascus Reuters Syrians make fuel from plastic waste Back to basics: a man checks the heat of a pipe pouring with fuel Reuters Syrians make fuel from plastic waste Khodor, 20, must keep an eye on the burning plastic inside the workshop in Douma Reuters Syrians make fuel from plastic waste A young man takes a container of the locally made fuel, which can be used for domestic heating and on farms and bakeries Reuters Syrians make fuel from plastic waste Abu Fahad on a rest break with his colleagues inside the workshop, where the air is heavy with toxic fumes Reuters Syrians make fuel from plastic waste Fuel drips into a container at the workshop. Most locals are glad of the family-run business, which has restored a degree of normality to the region Reuters Syrians make fuel from plastic waste Khodor extracts fuel from plastic in the workshop Reuters

Last week, the Syrian president visited the airfield to inspect weapons, personnel and armoured vehicles.

He was pictured sitting in the cockpit of a Russian Sukhoi SU-35.