BEIRUT (AFP) - Kurdish militia have driven the Islamic State in Iraq and Syria (ISIS) group from the Syrian border town of Kobane after months of heavy fighting, a monitor and spokesman said Monday, dealing a crucial blow to the militants.

Across the border in Iraq meanwhile, a top army officer announced troops had "liberated" Diyala province from ISIS extremists.

In Syria, the Kurdish advance marked the culmination of a battle lasting more than four months in which nearly 1,800 people were killed.

The Britain-based Syrian Observatory for Human Rights monitor said the Kurdish People's Protection Units (YPG) had pushed ISIS militants from all of Kobane.

They "expelled all Islamic State fighters from Kobane and have full control of the town", Observatory director Rami Abdel Rahman said. "The Kurds are pursuing some extremists on the eastern outskirts of Kobane, but there is no more fighting inside now."

The monitor said Kurdish forces were carrying out "mopping-up operations" against remaining ISIS forces in the Maqtala district, on the eastern outskirts of the town.

YPG spokesman Polat Jan also announced the news on his Twitter account, writing: "Congratulations to humanity, Kurdistan, and the people of Kobane on the liberation of Kobane." Mustafa Ebdi, an activist from the town, said that "fighting has stopped".

YPG forces are "advancing carefully in Maqtala because of the threat of mines and car bombs," he added.

The advance by Kurdish fighters came after 24 hours of heavy bombing by the US-led coalition fighting ISIS in Syria and Iraq.

In a statement, the Pentagon said the coalition had carried out 17 air strikes against ISIS positions in Kobane in the 24 hours from January 25 alone.

The targets included "tactical units" and "fighting positions" as well as an ISIS vehicle and staging areas, the statement said.

The loss of Kobane, also known as Ain al-Arab, would be an important defeat for ISIS.

The group has lost 1,196 fighters since it began its advance on the town on Sept 16, according to the Observatory.

At one point, the terrorist group looked poised to overrun Kobane, which lies on the Syrian-Turkish border.

It wielded sophisticated weapons captured from military bases in Syria and Iraq and committed hundreds of fighters to the battle.

But Kurdish forces gradually pushed back the extremists with the help of the US-led air raids and a group of fighters from Iraq's Kurdish peshmerga forces.

Analysts say the loss of Kobane is both a symbolic and strategic blow for ISIS, which set its sights on the small town in a bid to cement its control over a long stretch of the Syrian-Turkish border.

Since the group emerged in its current form in 2013, it has captured large swathes of territory in both Syria and Iraq.

It has declared an Islamic "caliphate" in territory under its control, and gained a reputation for brutality, including executions and torture. But its apparent failure in Kobane could put the brakes on its plans for expansion in Syria.

"Despite all that manpower, all that sophisticated weaponry, (ISIS) couldn't get the city, so it's a big blow for their plans and its a great achievement for the Kurds," Kurdish affairs analyst Mutlu Civiroglu said.

"Kobane sets an example on the ground, showing that when you have skilled fighters on the ground with the support of air strikes, this danger, these forces, can be stopped and eliminated."

Civiroglu said YPG forces would likely spend the next few days clearing Kobane before expanding outwards to surrounding villages captured by ISIS.

Civilians were largely spared in the fighting because the town's residents evacuated en masse, mostly across the border into Turkey, in the early stages of the battle.

Over the border in Iraq, the army announced another defeat for IS, with the recapture of Diyala province.

"We announce the liberation of Diyala from the (ISIS) organisation," Staff Lieutenant General Abdulamir al-Zaidi said. "Iraqi forces are in complete control of all the cities and districts and subdistricts of Diyala province."

The general said there would still be clashes however against ISIS in the rural Hamreen mountains, which stretch across multiple provinces, including Diyala.