(VOVworld) - Police say 10-20 people are involved in bomb and arson attacks on seven provinces. Police General Pongsapat Pongcharoen said the bomb and arson attacks last Thursday and Friday were all connected and carried out by a single mastermind.

Investigators work at the scene of an explosion in the resort town of Hua Hin, 240 kilometers south of Bangkok, Thailand Aug. 12. (AP/Jerry Harmer)

He said that authorities were putting together the jigsaw to identify the network behind the attacks that hit Hua Hin in Prachuap Khiri Khan province, plus six southern provinces, including Phuket. However, he did not identify or elaborate at this stage on the individual mastermind or the motives behind the attacks, which killed four people and injured dozens of Thais and foreigners.

The United Front for Democracy Against Dictatorship (UDD), or the red shirts, expressed their concern over the Thai government detaining its members after the bombings. Thai media said at least 5 UDD senior members were arrested for interrogation at military bases for alleged association with the multiple bomb and arson attacks in southern provinces.