Islamic State fighters pushed back on fronts in Syria, Iraq Forces of the self-declared Islamic State appeared Tuesday to have suffered another setback in the long battle for the northern Syrian city of Kobane, as Kurdish fighters there reportedly captured buildings housing a significant quantity of IS weapons and ammunition. The gain, reported by the Syrian Observatory for Human Rights, based in London, came a day after US Central Command said airstrikes by US warplanes over the weekend destroyed seven IS positions around Kobane. The strikes were part of a wider campaign against IS targets in Syria and Iraq that included attacks on a crude oil facility in Syria and near the key Iraqi oil refinery in Baiji. The sale of oil has been a crucial source of revenue for the IS jihadists in their campaign to set up a "caliphate" in the areas of northern Syria and Iraq under their control. A report late Monday to the United Nations Security Council estimates IS oil revenues to be $846,000 to $1,645,000 a day and urges the Security Council to order the seizure of all oil trucks entering and leaving IS-controlled territory, according to The New York Times. The report, by an expert panel appointed by UN Secretary-General Ban Ki-moon, also is seeking to ban the sale of antiquities, another revenue source, from areas under IS control. Also on Tuesday in Iraq, which has been struggling to regain territory lost in humiliating fashion last summer to a sustained IS onslaught, security forces entered the country's largest oil refinery for the first time in five months, Reuters reports, citing a police colonel and state television. If confirmed, the recovery of the Baiji facility could provide critical momentum for government forces charged with restoring stability in a country facing its worst security crisis since dictator Saddam Hussein was toppled in 2003. In this area, terrorists were stationed to the left and right. If God is willing, Baiji will be the main key to liberating each span of Iraq," [said] the commander of provincial security operations, Abdel Wahab al-Sa'adi. According to a separate Reuters report from Beirut, Kurdish fighters in Kobane seized six IS-held buildings and a large quantity of guns and ammunition. The buildings were in a strategic location close to Kobane's Security Square, where the main municipal buildings are based, said Rami Abdulrahman who runs the Observatory, a group that tracks the conflict using sources on the ground. The clashes killed around 13 Islamic State militants, including two senior fighters who had been helping to lead the militant group's assault on the town, he said. Kurdish forces appear to have made other gains in recent days of fighting. Last week they blocked a road Islamic State was using to resupply their forces, the first major gain against the jihadists after weeks of violence. The reported setbacks to the Islamic State, diplomatically and on the ground, followed the release Sunday of the latest beheading video, in which an IS executioner stands over the severed head of an American aid worker, Abdul-Rahman Kassig. As The Christian Science Monitor's Howard LaFranchi wrote Monday, some analysts noted that the video was devoid of the production quality of its predecessors, perhaps an indication of the pressure from US bombing and surveillance. But other counterterrorism experts see a different message in Sunday's video: IS has become so enthralled with its efforts to instill fear that it doesn't realize its actions are beginning to backfire. "We're continuing to see, including in this last video, a group that is so carried away with its own fanaticism and its own barbarity that it is not seeing how what is meant to compel people to cower and be fearful is actually having the opposite effect," says Wayne White, a former deputy director of the State Department's Bureau of Intelligence for the Near East. We're seeing how it's causing a stiffening of resistance and feeding a determination not to be dominated by these people. Recent polls in Arab countries indicate a rejection of Islamic State ideology, while recent fierce ground fighting has pushed IS fighters back from the northern Syrian town of Kobane. Even within Sunni Arab communities in Iraq - areas that in some cases initially showed support for IS aims - resistance to its advances has grown. This suggests to Mr. White that IS's barbarity might in the long run lead to its demise. "It says to me that IS is so blinded by its own heinous fanaticism that it doesn't get it," says White, now an adjunct scholar at the Middle East Institute in Washington.