Thai authorities say they are investigating whether bombings last week at several popular tourist destinations were related to long-term separatist violence in the country's far south.

Police have made no formal arrests in the bomb and arson attacks in seven towns that killed four people and wounded dozens. They told a news conference Monday that several people have been detained by the military for questioning, but declined to provide details.

The attackers' tactics have led to speculation that the bombings were carried out by Muslim separatists in Thailand's southernmost provinces who have staged a low-level insurgency since 2004.

National police chief Gen. Chakthip Chaijinda said Monday that there were similarities between the tourist spot bombings and those carried out by the separatists.