Kurdish fighters have retaken control of a strategic hilltop overlooking the town of Kobani near the border with Turkey.
News of the advance emerged after activists confirmed the US-led coalition had launched several air strikes on positions of Islamic State group militants in northern and eastern Syria.
The UK-based Syrian Observatory for Human Rights and the Local Coordination Committees say some of the air strikes targeted the eastern town of Mayadeen.
The Observatory said the bombardment hit oil refineries near Mayadeen, sparking a huge fire.
Idriss Nassan, a local Kurdish official from Kobani, added that intense air strikes had hit members of the Islamic State group around the town.
Mr Nassan said Kurdish militiamen captured the Tel Shair hill that overlooks the town and brought down the black flag of the Islamic State group.
Meanwhile, US president Barack Obama was to discuss the strategy today with military leaders from 20 countries, including Turkey, Arab states and Western allies.
Washington has faced the difficult task of building a coalition to intervene in Syria and Iraq, two countries with complex multi-sided civil wars in which most of the nations of the Middle East have enemies and clients on the ground. In particular, U. officials have expressed frustration at Turkey’s refusal to help them fight against Islamic State.
Washington has said Turkey has agreed to let it strike from Turkish air base; Ankara says this is still under discussion.
Nato-member Turkey has refused to join the coalition unless it also confronts Syrian president Bashar al-Assad, a demand that Washington, which flies its air missions over Syria without objection from Dr Assad, has so far rejected.
Agencies