In the Islamic State group's Syrian stronghold of Raqqa, sirens ring out whenever a warplane approaches as jihadists flee their posts and vehicles to hide, activists say.<br />A US-led coalition and Russia have stepped up air strikes on the jihadists' de facto Syrian capital since IS claimed to have downed a Russian passenger plane over Egypt's Sinai in October and the deadly jihadist attacks in Paris two weeks later.<br />A fellow activist who calls himself Abu Sham al-Raqqa added: "Whenever the jets fly over they set off the sirens to warn the fighters and the residents, and the problem is that the bombing is going on night and day."<br />According to Hashimi, IS has stopped transporting its oil products in 36,000-liter tankers and started using smaller, 4,000-liter vehicles after coalition and Russian airstrikes targeted hundreds of fuel trucks in Raqqa and Deir Ezzor, where it controls most oil fields.
