Islamic State fighters killed at least 145 civilians in an attack on the Syrian town of Kobani and a nearby village, in what a monitoring group described on Friday as one of the worst massacres carried out by the hardline group in Syria. Islamic State pressed a separate assault to capture government-held parts of the northeastern city of Hasaka, blowing up a security building and triggering a government appeal for all residents to take up arms. The United Nations said 60,000 people were reported to have fled the attack. Islamic State's twin attacks which began on Thursday showed the group returning to the offensive in Syria after two weeks of defeats at the hands of Kurdish-led forces, supported by U.S.-led air strikes. Earlier this week the Kurds advanced to within 50 km (30 miles) of Raqqa city, the group's de facto capital. The Kurdish YPG militia described the attack on Kobani as "a suicide mission" rather than an attempt to capture the town at the Turkish border. It said it fought intermittent gun battles on Friday with Islamic State fighters holed up in three locations. Islamic State has a record of conducting large scale killings of civilians in territory it captures in both Iraq and Syria, where it has proclaimed a caliphate to rule over all Muslims according to an ultra-hardline vision of Islam.