Thai Prime Minister Yingluck Shinawatra on Saturday ordered security agencies to provide better protection for officials and public in the restive southernmost region after a deputy governor was killed, Thai News Agency reported.

Issara Thongthawat, deputy governor of southern border province of Yala, died at hospital after a roadside bomb was detonated as his car travelled along Yala-Betong Road in Bannang Star district of Yala on Friday afternoon.

Yingluck expressed sorrow over the loss of Issara and ordered security agencies to step up measures to ensure the safety of officials and residents in the three southern border provinces.

The premier said that the death of Issara and a recent murder of a marine private in Narathiwat were outrageous actions which may affect the officials' morale.

The police suspected that the separatist militants were involved in both cases.

She vowed that the government would facilitate their work by providing modern equipment to assist their mission.

More than 5,000 people have been killed in Thailand's Muslim, ethnic-Malay dominated three southern border provinces -- Yala, Pattani, Narathiwat and four districts of Songkhla -- since separatist violence erupted in January 2004, according to Deep South Watch, which monitors the regional violence.