A pro-secession activist was killed on Friday by Yemeni security forces in the southern port city of Aden, a local source told Xinhua. The activist, identified as Mubarak al-Awlaki, was killed after a unit of the special security troops raided his house in Aden's neighborhood of Mansora, the source told Xinhua on condition of anonymity. An official of Aden's police authority told Xinhua the security forces cordoned off a house near a public square where several wanted activists were hiding. When the activists refused to turn themselves in and attempted to escape, the security soldiers opened fire and injured about three activists at the scene, the official said. The security operation came one day after some 35 kidnapped army soldiers were released as part of a prisoner swap deal between pro-secession gunmen and the Yemeni government under the mediation of tribal leaders and human rights groups. The soldiers were abducted during armed confrontations with the gunmen in the southern province of al-Dhalea last month. They were freed in exchange for the release of 40 secessionists jailed by Yemeni security authorities in the capital Sanaa, according to local government officials. North and South Yemen unified peacefully in 1990, but the relationship deteriorated in 1994. Calls for separation in the country's southern regions were renewed in 2007. Southerners have been complaining of being marginalized, particularly since they lost a four-month civil war in 1994. Pro- secession protests are on the rise in the south amid a worsening economic situation and allegations of discrimination in favor of northerners. Concerns have increased since the conflicts are creating instability in southern Yemen where al-Qaida could gain foothold.