Six killed in south Yemen on civil war anniversary ADEN (Reuters) - Four civilians and two soldiers were shot dead and 10 others wounded by security forces in the southern Yemeni port city of Aden Friday, southern separatists and an official said, as crowds gathered calling for the separation of the south. A local security official said three soldiers including a lieutenant were among those hurt at a festival to mark the anniversary of a violent struggle for an independent south which led to civil war and began in Aden on January 13, 1986. The crowd at the festival was shouting "Revolution! Revolution! Oh South!," witnesses said. Sunday, Yemen's cabinet proposed an immunity law to speed President Ali Abdullah Saleh's exit under a Gulf-brokered plan to end months of protests that have paralyzed the impoverished Arab state. Presidential elections are set for February 21. However, any successor to Saleh faces many challenges: a rebellion in the north, the southern separatist movement and al Qaeda's most active wing, based in Yemen. Thursday, at least four fighters from a Sunni Salafi Islamist group were killed in fighting with Shi'ite rebel fighters in northern Yemen. Analysts say Saleh was expected to leave Yemen for medical treatment after parliament approves the immunity bill. Reporting by Mohammed Mukhashaf; Writing by Martina Fuchs; Editing by Louise Ireland