Hafte Tir bombing

On 28 June 1981 (the 7th of Tir 1360 (Hafte Tir - هفت تیر) in the Iranian calendar), a powerful bomb went off at the headquarters of the Iran Islamic Republic Party (IRP) in Tehran, while a meeting of party leaders was in progress. Seventy-three leading officials of the Islamic Republic were killed, including Chief Justice Ayatollah Mohammad Beheshti,^[2][2][3] (who was the second most powerful figure in the revolution after Ayatollah Khomeini at the time). The People's Mujahedin of Iran or Mujahideen al-Khalq is thought to have been responsible for the attack.

• http://en.wikipedia.org/wiki/Hafte Tir bombing