"The IS have advanced southeast of Kobane and on the western front, from which the Kurdish Popular Defence Committees (YPG) have now retreated," said Syrian Observatory for Human Rights director Rami Abdel Rahman, using the Kurdish name Kobane to refer to the town.
"There are real fears that the IS may be able to advance into the town of Kobane itself very soon," Abdel Rahman warned.

The advances came hours after US-led forces carried out at least five strikes against IS positions south and southeast of the town, which the jihadists have been battling to take for more than two weeks, the Observatory said.
At least eight jihadists were killed in a strike on an IS tank east of the town on Wednesday, said the Britain-based Observatory, which relies on a wide network of sources inside Syria for its reports.
"Kurdish fighters on the front lines saw the bodies literally being thrown into the air" by the force of the blast, said Abdel Rahman.
Despite the air strikes, the jihadists continued to shell the town on the Turkish border from positions as little as three kilometres away.
"The fighting in the past 24 hours has been the fiercest since the IS began its offensive" a fortnight ago, said Abdel Rahman.
"There are real fears for the Kurds' capacity to resist, as the IS are using tanks and other heavy weaponry in their attack," he added.
Abdel Rahman said the vastly outgunned Kurdish fighters were forced by the jihadists' advance to retreat from the fight on the western outskirts of Kobane, in order to defend the edges of the town itself.
Kurdish security forces inside Kobane 'are preparing themselves for street battles' that would break out should the jihadists break the local fighters' last remaining line of defence, said Abdel Rahman.
Hundreds of poorly equipped Kurdish fighters are facing thousands of jihadists armed with tanks, heavy artillery and 220mm multiple rocket launchers.
Local Kurdish leader Anwar Muslim acknowledged the balance of forces favoured the jihadists.
"IS have brought in the weapons they seized from Mosul (Iraq's second city) and Tabqa airbase (in Syria's Raqa province)," he said.

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