ISTANBUL—Investigators have identified a suspect in a suicide bombing blamed on Islamic State, Turkey’s premier said Tuesday, as the country’s politicians pointed fingers over the attack.

The Monday blast left at least 32 people dead and wounded more than 100 in the town of Suruç, where socialist youth groups were preparing to cross the border to help rebuild Kobani. The Syrian city was ravaged in a four-month fight between Kurdish militias and the Islamist extremist group, which was ousted in January.

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