The Dutch foreign affairs ministry is warning people traveling to Thailand to avoid busy places and remain alert following several bomb attacks in popular holiday resorts.

The risk profile of the country has now risen from green to yellow, the ministry said on Friday after bombs on the island of Phuket and resort of Hua Hin killed at least four.

Three Dutch women and one man are among those injured in the blast in the resort of Hua Hin which left one Thai woman dead. Two of the Dutch women remain seriously ill in hospital, the foreign ministry said.

The Thai authorities on Friday arrested two men in connection with the bombings, describing them as incidents of local sabotage rather than IS related terrorism