TUNIS - At least eight Tunisian policemen and two Islamist militants were killed on Wednesday when they clashed during a raid by security forces in Sidi Bouzid in the south of the country, security sources and state television said.Tunisian authorities say Ansar al-Sharia, one of the Islamist militant movements to emerge since the country's 2011 uprising, is behind a string of attacks on security forces.Officials say it has ties to al-Qaida's North Africa affiliate.Wednesday's violence came just days after security forces killed 10 militants blamed for attacking Tunisian police patrols in a remote area near the Algerian border and killing two officers.Ansar al-Sharia is just one of the hardline Islamist groups based in North Africa. Tunisia's moderate Islamist-led government two months ago declared it a terrorist organization after blaming it for murdering two opposition leaders.