Mogadishu - Somali security forces on Thursday foiled a suicide attack by the Islamist group al-Shabaab, killing four of its members who were targeting a regional conference, a spokesperson for the national intelligence agency said.Three Somali soldiers were also killed, said a senior security source who asked not to be named.A suicide car bomber tried to get into a heavily guarded compound in the central town of Adado, where a conference was being held to adopt a constitution for the Galguduud and Mudug regions, said Mohamed Osman Yusuf, a spokesperson for the Somali National Intelligence and Security Agency."Security forces who were outside of the compound shot at the suicide car bomber, preventing him from reaching ... the conference hall," he said.Three other al-Shabaab fighters wearing Somali military uniforms were also fatally shot as they tried to storm the conference, Yusuf said. Three soldiers were killed in the shootout.Al-Shabaab claimed responsibility for the attack on the pro-insurgent website www.somalimemo.net. Delegates attending the conference were unharmed, Yusuf said.Galguduud and Mudug are in the process of creating a new state, which would form part of an emerging federal system in Somalia. It already includes the states of Puntland, Jubaland, South-West State and the breakaway Somaliland.