CAIRO (AP) — The Islamic State group in Egypt has claimed responsibility for a deadly attack on local tribesmen this week in the restive northern part of the Sinai Peninsula.

Egyptian officials had said earlier that Wednesday’s assault killed 10 members of the Tarabin tribe manning a checkpoint near a militant-stronghold south of the border town of Rafah.

The IS affiliate, known as Sinai Province, claimed in a statement on Friday that its fighters killed 15 “apostates” and wounded others who fled, leaving behind their SUVs.

Sinai’s powerful tribes have so far stayed on the sidelines of the battle between Egyptian authorities and the growing insurgency in Sinai led by the Islamic State group in recent years.

However, an open conflict between the Tarabin tribesmen and IS militants emerged in recent weeks.