October 12, 2015 11:39 PM EDT

There is “concrete evidence” linking Saturday’s twin blasts at an Ankara peace rally — the bloodiest terrorist attack in the country’s history, claiming around 100 lives — to the Islamic State of Iraq and Syria, Turkish authorities have told the Guardian.

ISIS has not publicly claimed responsibility for the bombing, and Turkish officials have not specified the nature of the information connecting the extremist group to the attack. However, authorities stressed the thoroughness of both their investigation, which the Guardian says has used a hundred surveillance personnel, and Turkey’s wider counterterrorism efforts, which have monitored ISIS cells in the country for months.

Authorities have also linked ISIS to July’s bombing in the southern city of Suruc.

In the wake of Saturday’s bombing, grief has melded with anger in the capital city. Many are blaming the state for failing to protect the demonstrators at the protest, which was held to decry the ongoing violence between the government and the militant Kurdistan Workers’ Party (PKK).

The rally was organized by the Peoples’ Democratic Party, which, despite its pro-Kurdish platform, denies charges that it operates in conjunction with the PKK.


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