The key Syria-Turkey border town of Kobane might fall to Islamic State (IS) fighters soon, an official there has told the BBC. A flag appearing to be that of Islamic State has been seen flying over a building on the eastern edge of Kobane. The official, Idriss Nassan, said IS was now in control of Mistenur, the strategic hill above the city. Kobane has seen intense fighting over the past three days as Syrian Kurds try to defend the town. US-led forces have been conducting air strikes on IS positions in the area to try to slow their advance. There were unconfirmed reports of another such strike overnight. The IS militants have been besieging the town for nearly three weeks. More than 160,000 Syrians, mainly Kurds, have fled across the border since the offensive was launched.