BEIRUT (AFP) - At least 50 extremists of the Islamic State in Iraq and Syria (ISIS) have been killed in the past 24 hours in clashes, suicide bombings and US-led air strikes in Syria's Kobane, a monitor said Sunday.

The Syrian Observatory for Human Rights said the number of deaths was one of the highest daily tolls for the Sunni Muslim ISIS since it launched an assault on the strategic town on the Turkish border in September. The siege has become a widely-watched battle in the US-led war on the terrorist group.

The Britain-based Observatory said at least five of those killed were suicide bomb attackers, two of them involved in attacks on the border crossing that separates Kobane from Turkey.

Another 11 were killed in clashes that ensued between Kobane's Kurdish defenders and the insurgents at the border after the bombings, but there was no breakdown for the remaining toll.

The group also said 11 Kurdish fighters were killed in the same period in Kobane, along with one Syrian rebel fighter backing the Kurdish forces.

ISIS began advancing on Kobane on September 16, hoping to quickly seize the small border town and secure its grip on a large stretch of the Syrian-Turkish border.

At one point, it looked set to overrun the town, but Kurdish Syrian fighters, backed by US-led coalition air strikes and an influx of Iraqi Kurdish peshmerga forces, have held back the group.

For now, the town remains roughly evenly divided between ISIS and Kurdish control.