NAIROBI (AFP) - A blast ripped through shops in central Nairobi Monday, wounding dozens in what the prime minister called a “terrorist” attack despite initial police reports of an accidental cause. Speaking at the charred and wrecked small shopping complex in Nairobi’s commercial heart, Raila Odinga contradicted the country’s police chief, who had earlier said the explosion was caused by an electrical fault. “This is terrorism... this is a heinous act, we are under threat but we will not be cowed,” Odinga said. “The lives and property of Kenyans are precious and must be protected, we condemn the terrorists and tell them that their days are numbered.”At least 28 people were wounded, four of them in a critical condition, the Kenya Red Cross said.Kenya has been hit by a wave of grenade attacks the police have repeatedly blamed on Somalia’s Qaeda linked Shebab insurgents or its supporters.Last month the hardline Shebab warned Kenya of revenge attacks for sending tanks and troops into Somalia in October.