Four people were killed and 27 injured in a collision between a bus, truck and taxi near Havana, the third serious bus wreck reported in Cuba in the past week, Cuba's state-run radio said today. A Radio Rebelde broadcast monitored in Miami today did not disclose when the three-way accident occurred or what caused it. The report said 15 of the injured victims were in serious condition. In a June 25 accident, a train and bus collided near Havana, killing at least 27 people, most of them teens, and injuring about 80 other people, a broadcast said. The day before, Cuban radio reported that 10 people died and 21 were injured when a bus and tractor-trailer collided along Cuba's main highway after the bus driver was blinded by lights of oncoming traffic.