Songkhla: A bomb blast in Thailand's Sadao district left three railway workers dead and four of their colleagues hurt, media reports said on Tuesday.

Local police were informed of the repeat explosion at 6.24am. It happened at the site where freight train no. 707 was derailed in the first attack, in tambon Tha Pho between Khlong  Ngae and Padang Besar train stations, reports Bangkok Post.

The bomb targeted a temporary salvage command post about 400 metres from Saturday's blast spot, the newspaper reported.

The deceased workers were identified as Yingsak Chumtree, Phumphan Phetsuka and Nawarit Suwanchatree.