NAIROBI — The Dutch embassy in Kenya has warned of a possible attack against foreigners, shortly after police in the east African country discovered a large quantity of explosives on a bus in the capital Nairobi. Kenya has seen a series of grenade and gun attacks since October 2011, when its troops went into neighboring Somalia in pursuit of Al-Qaeda-linked insurgents it blames for kidnapping security personnel and Western tourists from its territory. Kenyan police said on Wednesday they had discovered 403 rolls of ammonium nitrate explosives inside boxes apparently containing books on a bus in Nairobi, but had few details about who was behind the parcels. Government spokesman Muthui Kariuki said some embassies had been spooked by Wednesday's discovery, but he was adamant that there was no threat to foreigners in Kenya. — Reuters