The "Islamic State of Iraq and Syria" on Thursday (May 11th) claimed its elements had the previous day killed 15 tribesmen in North Sinai, Egypt's Ahram Online reported.
Security sources on Wednesday confirmed 10 tribesmen were killed in clashes.
In a statement published by its media arm, Amaq, ISIS claimed it had ambushed a group of “pro-Egyptian army” tribesmen at a checkpoint.
The group claimed it had killed Salem Abu Lafy, a leading figure in al-Tarabin tribe, one of Sinai's largest, during the ambush.
On Wednesday the Sinai Tribes Union, a coalition of local tribes opposed to ISIS, confirmed Abu Lafy's death during fighting with militants.
The union vowed to avenge his death and the death of other members killed. It warned that the tribes would punish those who support ISIS, harbour its elements or withhold information about it from the tribes or the authorities.
In late April, al-Tarabin, Sawarka and Rumeilat tribes publicly declared they would “cleanse” North Sinai of the group, in co-operation with the Egyptian armed forces, reinforcing earlier statements of support.
Earlier in the week, UK travel company Thomas Cook said it had removed the south Sinai resort of Sharm el-Sheikh from its winter 2017-2018 and summer 2018 holiday and flight programmes.
