Three railway workers died while four others were injured today in a repeat bombing at the site where a cargo train was attacked three days ago in terror-ravaged southern Thailand.

The workers were caught in the blast that hit the Sadao district of Songkhla province at around 6:24 am - just three days after another bomb went off along the same tracks.

Police identified the casualties as Yingsak Chumtree, Phumphan Phetsuka and Nawarit Suwanchatree, who were employed at the Hat Yai district of the State Railway of Thailand.

The four wounded were named as Noppadol Panma, Deeden Khongsom, Chatchai Nitchalanoont and Theerapong Nukhong.

One of the survivors, Deeden, said: 'It happened when we were walking back from the first blast site. The explosion threw us all in different directions, so I panicked and ran for my life.'

The group were assigned to work at the scene to repair the railway and clear several train cars, which derailed last Saturday after an IED bomb exploded and severely damaged a freighter delivering rubber sheets to Malaysia.

Police and army officials have now secured the area while a bomb squad trawls through the surrounding land to check for more devices.

Islamic separatist terror attacks happen regularly in the three southernmost provinces of Thailand next to the border with hardline neighbors Malaysia. However, they rarely target civilians and are geared towards hitting Thai state employees and infrastructure.

The three provinces of Thailand - Yala, Pattani and Narathiwat - have been blighted by terrorism for several decades, dating back to a deal in 1909 between the British Empire to incorporate the Muslim region into the main country of Siam.

The area's culture is more similar to Malaysia and dramatically different to Buddhist Thais causing decades of tension culminating in the emergence of separatist groups fighting for independence in the 1960s.

The struggle has continued ever since with more than 7,290 people killed between January 2004 and October 2021. There were an average of 38.8 incidents and 36.7 casualties a month in 2021, according to data from Deep South Watch.

The British Foreign & Commonwealth Office warns against all but essential travel to the region while Canada's government warns its nationals to 'avoid all travel' to the three provinces.