From Beirut, Carlos participated in the planning for the attack on the headquarters of OPEC (Organization of the Petroleum Exporting Countries) in Vienna. On 21 December 1975, he led the six-person team (which included Gabriele Kröcher-Tiedemann) that attacked the meeting of OPEC leaders. The team took more than 60 hostages and killed three: an Austrian policeman, an Iraqi OPEC employee and a member of the Libyan delegation. Carlos demanded that the Austrian authorities read a communiqué about the Palestinian cause on Austrian radio and television networks every two hours. To avoid the threatened execution of a hostage every 15 minutes, the Austrian government agreed and the communiqué was broadcast as demanded.