A supporter of the separatist Southern Movement is carried Thursday to an ambulance after he was injured during clashes with security forces in the southern Yemeni port city of Aden, ahead of planned rallies to mark the first anniversary of ex-president Ali Abdullah Saleh's ouster. — Reuters ADEN — Security forces opened fire to disperse secessionist protesters in the south Yemen port of Aden and a nearby town on Thursday, killing at least six people, medical sources and witnesses said. Mass unrest that ousted authoritarian president Ali Abdullah Saleh a year ago caused widespread disorder in which separatist agitation in south Yemen has revived almost 20 years after it was suppressed in a brief civil war won by the north. Witnesses said the security forces shot at dozens of secessionists in Aden as they staged a rally against Saleh's successor, President Abd-Rabbu Mansour Hadi, a northerner, on the anniversary of his election. A local security official said one person had died, without elaborating. Witnesses and medical sources said four people were killed, all men, with about 40 people wounded. In Al-Dalea, a security official and an activist were killed in clashes involving southern separatists, medical sources and witnesses said. Spokesmen for the security services and the government were not immediately available for comment. North and South Yemen unified in 1990 when the collapse of the Soviet Union undermined the communist south's economy. But political harmony was short-lived and an attempted southern secession in 1994 prompted civil war. Hadi was appointed in February 2012 after popular protests forced Saleh to step down under a deal brokered by Yemen's wealthy Gulf Arab neighbors. The protests left the Arab world's poorest country in a state of upheaval, emboldening one of Al-Qaeda's most active wings, Yemen-based Al-Qaeda in the Arabian Peninsula (AQAP), and reviving separatist sentiment in the south. Southern Yemenis, complaining of discrimination by the north, favor creating another independent socialist state. The separatists gathered Thursday to protest against the holding of celebrations by Hadi's supporters in Aden, the former capital of independent South Yemen, intended to mark the completion of his first year in power. A witness said the military brought in armored vehicles to Aden's Khor Al-Maksar and Crater neighborhoods where most of the protests were taking place. Tackling lawlessness in Yemen, which lies near important oil shipment routes and flanks the world's biggest oil exporter Saudi Arabia, has become an international priority. Washington and other Western governments regard AQAP as one of the most dangerous offshoots of the militant network. The group has planned attacks on international targets including airliners. — Reuters