Kurdish forces took control of the Syrian town of Kobani on Monday after driving out Islamic State fighters, a monitoring group and Syrian state media said, although Washington said the four-month battle was not yet over.

Some Islamic State supporters took to Twitter to say the fight for Kobani, a focal point of the international struggle against the ultra-hardline Islamist group, was still raging.

Islamist militants launched an assault on the predominantly Kurdish town last year, using heavy weapons seized in Iraq and forcing tens of thousands of locals into exile.

The Britain-based Syrian Observatory for Human Rights said the Syrian Kurdish People's Protection Units (YPG) had retaken the town, close to the Turkish border, but were proceeding carefully in the eastern outskirts where Islamic State had planted mines before fleeing.

"I can see the YPG flag flying over Kobani. There are the sounds of jets flying above," said Tevfik Kanat, a Turkish Kurd who rushed to the border with hundreds of others, including refugees from Kobani, after hearing about the advance.

"People are dancing and singing, there are fireworks. Everyone feels a huge sense of relief," he said by telephone.

The Islamic State still has fighters in hundreds of nearby villages, and called on supporters on Monday to target people in the West with whatever weapons they could lay their hands on.

U.S.-led forces have carried out almost daily air strikes on Islamic State positions around the town, known as Ayn al-Arab in Arabic. It has been a frontline in the battle against the group that has captured expanses of Iraq and Syria and proclaimed an Islamic caliphate.

"The people of Ayn al-Arab were able to expel the terrorist organization Daesh from their town and control it almost completely," Syrian state news agency SANA said, citing local sources.

The Pentagon said it could not declare the battle for Kobani over, but said the Kurds had the upper hand.

"I am not prepared to say the battle there is won. The battle continues. But as of now, friendly forces ... I believe, have the momentum," spokesman Colonel Steve Warren said.

U.S. Central Command said in a statement that anti-Islamic State forces controlled about 90 percent of Kobani.

U.S. coordination

Photographs posted on social media showed male and female Kurdish fighters shaking hands and Kurdish flags flying over recaptured territory. Reuters could not immediately confirm the pictures' authenticity.

Some militant supporters denied there had been a retreat.

"It is untrue (what) had been said in the media about the takeover ... still fierce battles ongoing," one tweeted.

Months of fighting in Kobani prompted Iraqi Kurdish forces known as peshmerga to travel to Syria to support the YPG after the United States asked Ankara to let them join the battle.

The struggle for Kobani is the only publicly declared example of U.S.-led forces closely coordinating militarily with a ground force to battle Islamic State.

The United States says it wants to train and equip non-jihadist groups to fight Islamic State elsewhere in Syria, but fighters say there is uncertainty surrounding the plans.

The recapture raises the question of what Islamic State will do next. Its fighters halted a westwards advance in the countryside north of Aleppo in September when it launched the offensive against Kobani.

In the east of the country, the Syrian army and pro-government militia recaptured an area north of Deir al-Zor military air base from Islamic State fighters, killing at least 19 of them, the Observatory said.

The airport is one of the last remaining government strongholds in eastern Syria and Islamic State has been trying to capture it for weeks. Government forces have held on to the base and parts of the provincial capital.

In an audio clip posted online on Monday, Islamic State spokesman Abu Mohammad al-Adnani said supporters should attack Westerners with whatever weapons they had, "whether an improvised explosive device, bullets, a knife, car bomb or a fist".

"We repeat a call to followers in Europe and the infidel West to target the crusaders in their own lands and wherever they are," he said, praising attacks in Paris, Ottawa and Sydney.