Extremist fighters with the self-styled "Islamic State" ("IS") were driven out of Kobani on Monday, activists and Kurdish officials said, in what would be a key coup for forces opposing the Sunni Islamist militia.

"The Islamic State is on the verge of defeat," said Kurdish official Idriss Nassan, speaking from Turkey near the Syrian border. "Their defenses have collapsed and its fighters have fled."

The British-based Syrian Observatory for Human Rights also reported the partial IS retreat out of Kobani, officially known as Ain al-Arab, but noted some sporadic fighting.

"The Kurds are pursuing some jihadis on the eastern outskirts of Kobani, but there is no more fighting inside now."

Months of fighting have leveled Kobani's old market street

Nassan said he was preparing to visit the border town on Tuesday, saying he expected it to be completely freed by then.

Since mid-September, the battle for Kobani has reportedly claimed some 1,600 lives. According to figures from the UK-based Observatory watchdog released earlier this month, "IS" had lost 1,075 fighters in its bid to control the city, with 459 Kurdish fighters and 32 civilians also killed.

Islamic State fighters first began capturing villages close to Kobani in September, before thrusting into the town itself, pushing thousands of refugees out of Kobani and across the border into Turkey.

The town became something of a symbol for international intervention to stop the IS advance; US Secretary of State John Kerry said after the US-led bombing strikes against IS were announced that it would be "morally very difficult" not to help Kobani.

A combination of US-led airstrikes and the arrival of Kurdish peshmerga fighters from Iraq helped turn the tide in the battle for Kobani, with the peshmerga evening out IS' earlier artillery superiority.

Kurdish official Nassan said that coalition airstrikes had intensified in recent days to lay the groundwork for his fighters' final push on IS positions to the south and east of the town. Since the US airstrikes began on September 23, an average of around six air strikes per day have targeted fighters in or near Kobani. Four-fifths of all coalition airstrikes in Syria, as opposed to Iraq, have been in or around the town.

msh/kms (AFP, AP)