Islamic State fighters continued to shell the Syrian town of Kobani on the border with Turkey on October 4 despite a new wave of U.S-led air strikes.
U.S.-led coalition warplanes had struck at IS targets overnight to halt the insurgents' advance and barrages were less intense than the previous day.
Previous coalition air strikes have failed to stop the insurgent offensive and an estimated 180,000 people have fled across the border into Turkey to escape the fighting around Kobani.
Kobani's capture by IS fighters would provide a direct link between areas under their control in Syria's Aleppo and their stronghold in Raqqa to the east.
The Syrian Observatory for Human Rights also said on October 4 that 25 IS fighters were killed by air strikes near the town of Shadadi in the northeastern province of Hasakeh.
Meanwhile, Turkish Kurds and Kurdish refugees from Syria clashed with Turkish security forces on the border between the two countries.
Troops used tear gas and water cannon to disperse protesters who are angry about the situation in Syria and accuse Turkey of allowing IS militants to cross the border in order to fight Kurds there.
The fighting around the Kobani has prompted the exodus of some 300,000 people in the past weeks. Many have sought refuge in Turkey.
The developments come amid a Turkish-U.S. row over Ankara's alleged support for IS militants.
Speaking at Harvard University on October 3, U.S. Vice-President Joe Biden criticized Turkey and U.S. allies in the Arab world for having supported Sunni militant groups such as the IS.
Turkish President Recep Tayyip Erdogan on October 4 responded to reports about those remarks, telling journalists: "If Biden has used such expressions, then Biden is history for me from now on. No-one can accuse Turkey of having supported any terrorist organization in Syria, including IS."
Biden on October 4 said in a statement he had called apologized to Erdogan over the comments.
"The vice president made clear that the United States greatly values the commitments and sacrifices made by our allies and partners from around the world to combat the scourge of ISIL, including Turkey," said the statement.
Separately, United Arab Emirates Minister of State for Foreign Affairs Anwar Gargash also demanded an official explanation for Biden's remarks, which he said had created "a negative and untrue impression about the role of the UAE."
Based on reporting by AFP, AP, Reuters, and dpa