The Syrian Observatory for Human Rights said the jihadists were killed after entering an eastern neighbourhood of the town and coming under attack by Kurdish fighters from the People's Protection Units (YPG).
"The jihadists died in an ambush by the YPG after they entered Street 48 in the east of Kobane overnight," Observatory director Rami Abdel Rahman said.
The attack appeared to be the first time that IS fighters had entered the town since they began advancing on Kobane nearly three weeks ago.
IS has seized much of the area around Kobane, also known as Ain al-Arab, since it began its advance, prompting some 186,000 local residents to flee across the border into Turkey.
But Kurdish fighters inside the town have thus far held off a full-scale offensive of Kobane by the group.
The jihadist group is hoping to seize the town to cement its group over a long stretch of the border between Syria and Turkey.