In the lead-up to the Day of Ashura, which involves large numbers of pilgrims travelling, some to Najaf, for Shiite festivals, the Iraqi officials were said to have discovered a plot to assassinate the Grand Ayatollah Ali al-Sistani and other Shia religious leaders by the insurgents. Alleged plans called for the insurgents to disguise themselves as pilgrims and suddenly open fire, in attempts to assassinate as many leading Shiite clerics as possible and cause overall disruption of the holiday. Violent attacks have occurred in Najaf during previous Ashura festivals (see Ashura massacre).