Kenya will not pull troops out from Somalia until security is restored, Prime Minister Raila Odinga said Monday, a day after 17 people died in the worst attack in a decade that he blamed on Somali Islamists. Meanwhile four foreign aid workers abducted Friday from Kenya’s Dadaab refugee camp complex – the world’s largest and home to some 465,000 mainly Somalis fleeing their lawless nation – were released safely Monday in Somalia. The aid workers, with the Norwegian Refugee Council, come from Canada, Norway and the Philippines, the fourth being a dual national from Canada and Pakistan. Speaking in the eastern Kenyan garrison town of Garissa, where masked gunmen Sunday hurled grenades into two churches before firing guns into the congregation, Odinga offered a defiant message to the Al-Qaeda-linked Al-Shabaab. “Surrender is not an option for us, because if we leave Somalia, anarchy will set in and will spill over the borders,” Odinga told reporters. “Kenya will stand together even as Al-Shabaab acts in desperation ... Al-Shabaab are reacting to the progress made by our forces in Somalia. We shall stand united and in solidarity.” Odinga also voiced concern that Al-Shabaab, who profess allegiance to Al-Qaeda “could link up with other terrorist groups like Boko Haram in Nigeria,” although he gave no further details. Kenya has suffered a spate of gun, grenade and bomb attacks since sending troops into Somalia last October to target Al-Shabaab rebels.