Islamic State casualties in the Syrian city of Kobani are mounting in a war of attrition with Kurdish fighters, according to a rights monitor and analysts.

More than 1,150 people, including at least 712 members of Islamic State, have been killed in clashes there over the past two months, the U.K.-based Syrian Observatory for Human Rights said in a statement. The tally could not be independently verified.

Bolstered by the arrival this month of better-armed Kurdish forces from Iraq, known as peshmerga, and sustained aerial bombing of Islamic State by the U.S., Kobani's defenders have repelled militant advances and accomplished some "minor achievements" along the city's northern and western fronts, said Rami Abdurrahman, SOHR's head.