ISTANBUL — Responding to growing anger over the government’s failure to prevent the terrorist attack last week that killed nearly 100 people, Turkey’s Interior Ministry fired several security officials on Wednesday, including the police chief in Ankara, the capital, where the attack occurred.

The firings came amid widespread reports in the Turkish news media that the government had zeroed in on two suspects with links to the Islamic State, the Sunni militant group in control of large areas of Syria and Iraq. According to the reports, one of them is believed to be a brother of the suicide attacker who killed at least 32 people in July at a gathering of Kurdish activists in the southeastern city of Suruc, and who the government said had links to the Islamic State. If the men are related, critics are likely to ask why the intelligence services did not foresee the Ankara bombings.

Without naming the suspects, Prime Minister Ahmet Davutoglu said at a news conference on Wednesday that both the Islamic State and the Kurdistan Workers’ Party, the separatist Kurdish militant group, were behind Saturday’s twin bombings in Ankara, modern Turkey’s deadliest terrorist attack.

Experts, though, said it was unlikely, even implausible, that the P.K.K., as the Kurdish party is known, was involved, given that the target of the attack was a peace rally organized in part by Kurds, a minority in Turkey whose rights the group has championed for more than three decades. In addition, the Islamic State has been fighting the P.K.K. in Syria and Iraq, making it more likely that Islamic State militants would target a gathering of Kurds within Turkey.