NEW : Interim president chooses new prime minister . Mohamed Ghannouchi 's resignation comes after three people were killed during protests . Protesters were demanding that he and the parliament step down . The opposition said it would not accept a government led by him or his party, which is known for its harsh treatment of political opponents.
NEW : Interim president chooses new prime minister . Mohamed Ghannouchi 's resignation comes after three people were killed during protests . Protesters were demanding that he and the parliament step down . He said he did n't want to make a decision that would cost lives .