 In 1987, Libya began production of mustard gas at a facility in Rabta, although publicly denying it was stockpiling chemical weapons, and unsuccessfully attempted to develop nuclear weapons.The period also saw a growth in domestic Islamist opposition, formulated into groups like the Muslim Brotherhood and the Libyan Islamic Fighting Group.A number of assassination attempts against Gaddafi were foiled, and in turn, 1989 saw the security forces raid mosques believed to be centres of counter-revolutionary preaching.