Saudi Arabia's Interior Ministry says militants linked to the Islamic State group were behind a surprise attack this month that killed seven Shiites in the kingdom's east.

Interior Minister spokesman Mansour al-Turki says an investigation found that the attack was planned by a 77-person terrorist cell.

Al-Turki said in a statement Monday carried by the official Saudi Press Agency that the militants received orders from abroad. He says police killed three suspects, two of them Saudi and the third a Qatari. He says they seriously wounded a fourth Saudi and arrested the rest.

The Islamic State group's leader Abu Bakr al-Baghdadi has called on his supporters to launch attacks inside Saudi Arabia, which is part of the U.S.-led coalition conducting airstrikes against the group in Iraq and Syria.