Ouagadougou - Militants who shot and killed 18 people at a restaurant in Burkina Faso's capital most likely came from Mali, a security source in Ouagadougou told AFP on Wednesday. "Looking at the tactics of the assailants, their physical traits, they probably came from northern Mali or closer to the border" with Burkina Faso, an army officer said on condition of anonymity.At least eight foreigners were killed at a Turkish restaurant in Ouagadougou on Sunday night when gunmen attacked diners on its terrace. No group has so far claimed responsibility but Burkina Faso has witnessed a string of such attacks blamed on Islamist extremists. The landlocked country shares a largely lawless border region with Mali, where jihadist fighters frequently ambush security forces. Ouagadougou prosecutor Faso Maiza Sereme has said Sunday's attack bore similar hallmarks to last year's assault on a hotel and cafe in the capital that killed 30 people and wounded more than 70.That attack was claimed by Al-Qaeda in the Islamic Maghreb (AQIM). "The fact that the attack hasn't been claimed just suggests that it's an isolated act that could be linked to Ansarul Islam or AQIM," the officer said.Ansarul Islam is active in northern Burkina Faso and has claimed responsibility for several recent attacks, including one that killed 12 soldiers in December. Security Minister Simon Compaore said all possibilities were being investigated. "The inquiry could take a long time and we need to work with other countries," he said.