Police : Blasts were caused by grenades , two arrested . Two explosions killed 10 people in central Nairobi , officials said . Kenyan authorities described the warnings as `` unfriendly acts '' and said security remains a top priority . Score: 6 Attacks come after U.S. , Australia , UK issue travel alerts .
Police : Blasts were caused by grenades , two arrested . Two explosions killed 10 people in central Nairobi , officials said . Score: 6 Attacks come after U.S. , Australia , UK issue travel alerts .