MANILA, July 7 (Reuters) - A powerful blast ripped through a commuter bus at a transport terminal on the southern Philippine island of Mindanao on Saturday, a police commander said. Robert Kuinisila, police chief in South Cotabato province, said there were no reported injuries because the passengers had got off the bus when a crude bomb went off around 5:30 p.m. (0930 GMT). "We're still investigating whether this was the handiwork of extortionists or terrorists," Kuinisila told reporters. "Let's not speculate, we'll identify the perpetrators based on the pieces of evidence we would gather on the scene." Last month, 10 people were killed when a bomb exploded inside a Davao City-bound bus as it was leaving its terminal in Bansalan town in Davao del Sur, the third bus to be destroyed by crude bombs blamed on Islamic militants. Last month, the U.S. embassy in Manila issued an advisory, warning its citizens to stay away from crowded bus stations and public markets in three key urban centres on Mindanao due to threats of bombings.
