Russia on Wednesday said its planes will attack any tanker trucks travelling through territory belonging to the Islamic State (ISIS) group in Syria, as Moscow looks to ratchet up pressure on the jihadists.

Today a decision was taken according to which Russian warplanes are now flying on a so-called ‘free hunt’ against tanker trucks carrying oil products belonging to terrorists in areas controlled by ISIS,” senior Russian military official Andrei Kartapolov was quoted as saying by Russian news agencies.

Kartapolov said that Russian aviation had already destroyed some 500 fuel trucks over the past “few days” transporting oil from Syria to refineries in Iraq.

“This has considerably lowered the ability of the fighters to illegally export energy products and their income from contraband oil,” he said. Revenues from oil smuggling are a key part of ISIS financing.

The Pentagon revealed on Monday that the US took out 116 ISIS fuel trucks in a single airstrike.

Russia for a second day running sent long-distance bombers to attack targets in the ISIS-held Raqa and Deir Ezzor provinces.

Other strategic bombers flying over Russian territory fired cruise missiles at the Idlib and Aleppo provinces.

Planes from the Russian base in Syria have bombed some 150 targets across the war-torn country.

Moscow pledged to ratchet up its strikes in Syria on Tuesday after confirming for the first time that a bomb brought down its passenger jet over Egypt last month.

Russia has been flying a bombing campaign in Syria since late September in support of forces loyal to Bashar al-Assad.

AFP contributed to this report.