Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. March 12, 2012 In Kenya, Four Arrested Over Grenade Attacks VOA News A policeman inspects pockets of a man killed in an explosion in Kenya's capital, Nairobi, March 10, 2012. Photo: Reuters A policeman inspects pockets of a man killed in an explosion in Kenya's capital, Nairobi, March 10, 2012. Kenyan police say they have arrested four people in connection with deadly grenade attacks in Nairobi blamed on the Somali militant group al-Shabab. Officials said Monday they had arrested Slyvester Opiyo and three teenagers and brought them in for questioning. Opiyo was previously arrested in December on suspicion of having links to al-Shabab. Officials accuse attackers of hurling grenades at the outdoor terminal of a major bus station in the capital on Saturday evening. The attack killed at least six people and injured about 60. This is the latest in a string of gun, bomb and grenade attacks that have killed dozens of people since Kenya sent troops into Somalia in October to fight al-Shabab. The group recently formalized an alliance with al-Qaida, and East African governments have declared the militants to be a regional threat. Al-Shabab has been trying to overthrow Somalia's government and turn the country into a strict Islamic state. The group claimed responsibility for bombings in Uganda's capital that killed more than 70 people in July 2010. No one has claimed responsibility for Saturday's attack. Some information for this report was provided by AP and AFP. .