The move is drawing anger from rights groups as the deadline to register photos nears.

An order for mobile phone users in Thailand's restive south to submit a photo of themselves for facial recognition purposes is causing uproar from opponents who see it as further curtailing the rights of the Muslim-majority population.

But an army spokesman on Wednesday defended the move, saying the facial identification scheme is needed to root out insurgents deploying mobile phone-detonated home-made bombs.

Thailand's three southernmost states -- Yala, Pattani, and Narathiwat -- have since 2004 been rife with conflict between Malay-Muslim rebels and the Buddhist-majority Thai state, which annexed the region around a century ago.

The tit-for-tat violence has claimed around 7,000 lives, mostly civilians of both faiths, and security forces have detained individuals suspected of being separatist rebels without warrants in the past.

Now telecoms companies are requiring all users of the region's 1.5 million mobile numbers to submit a photo of themselves for facial recognition purposes following orders from the army -- a move that is drawing anger from rights groups as the deadline to register photos nears.

A military spokesman defended the move on Wednesday, saying it was necessary to identify perpetrators who use mobile phone reception to set off home-made bombs.

"In cases where the attacker uses a SIM card to detonate a bomb, we can trace the perpetrator," said Colonel Watcharakorn Onngon, deputy southern army spokesman.

Registration ends on October 31, and anyone who fails to submit their photo in the three southern provinces and four districts in neighbouring Songkhla province will have their mobile reception cut off, he said.

Junta leader-turned-premier Prayut Chan-O-Cha on Tuesday also said the scheme provides "evidence" about who the real owner of each SIM card is.

"People in the south are not complaining... they know it truly helps reduce violence," he said.

The Muslim-majority south and rights groups have long accused the Thai state of heavy-handed sweeps of the Malay-Muslim populations, raising tensions in communities who feel targeted in their homes.

Using such "flawed" facial recognition technology usually leads to "racial profiling and, in turn, wrongful arrests", according to a statement by rights group Cross Cultural Foundation Tuesday.

"The risks of racial discrimination may erode public trust in policing the region," it said.

While the rest of Thailand is not subjected to the same requirement of submitting photos, Watcharakorn said people with unregistered SIMs travelling to the three provinces will have no cell access.