Mombasa bar hit by grenade attack "This is to alert all US citizens in Kenya, or planning to travel to Kenya in the near future, that the US embassy in Nairobi has received information of an imminent threat of a terrorist attack in Mombasa," a statement said. One of the Iranians was detained Wednesday in Nairobi, the other Thursday in Mombasa, police said. Police in Nairobi have also seized bomb ingredients from two young men who were stopped during a routine patrol, according to a police officer who spoke on condition of anonymity Saturday. The call to shun Kenya's second city which lies on the Indian Ocean is likely to deal a further blow to tourism, a key revenue sector for the east African nation that only recently recovered from the violent fallout of a disputed 2007 presidential election. Since Kenya invaded southern Somalia in October 2011 to help oust al-Qaeda-linked Shabaab insurgents, it has seen a wave of grenade attacks and kidnappings of foreign tourists blamed on the Shebab or their supporters.