A bomb planted along rail tracks in southern Thailand exploded early Wednesday, killing three police officers, a day after a wave of at least 100 attacks by suspected Muslim separatists in the restive south, police said.

Another officer was injured in the attack in the Chana district of Songkhla province, which was believed to have targeted police who conduct daily inspections of tracks before the departure of morning trains, said police Lt. Col Sompien Eksomya.

The blast occurred at about 6:30 a.m. (2300 GMT).

More than 1,500 people have been killed in Thailand's three Muslim-dominated provinces — Yala, Pattani and Narathiwat — since a resurgence of a violent Islamic separatist movement in January 2004. Songkhla's Chana district is adjacent to Pattani province.

CountryWatch: Thailand