A group of 15 suspects detained by the Thai military investigating last week's deadly tourist resort attacks was not involved in the blasts, police said Friday, adding to confusion surrounding the case.

The junta said Thursday the detainees had been held during their investigation into the bombing spree, which hit tourist towns in the south, killing four and wounding dozens, including Europeans.

But on Friday police officials said the group -- many of whom are elderly -- had instead set up an illegal network aimed at overthrowing the regime and were unconnected to last week's attacks.

Thailand's deputy junta chief also appeared to back that assertion.

The bombs were highly unusual in a country where foreigners and tourist towns are rarely caught up in the country's frequent bouts of political violence.

Investigators have been under pressure to make quick arrests given tourism is so crucial to the economy.

The group appeared at a Bangkok police station on Friday escorted by soldiers -- the first time they have been seen in public -- to hear the charges against them.

Two are women and many of the men are in their 60s and 70s.

Thai media had run multiple reports quoting anonymous investigators as saying the group helped coordinate the recent attacks.

But Major General Chayaphol Chatchaidej, a senior official at the Office of Police Strategy who was at the police station to receive the suspects, told reporters they were not involved.

"There is no evidence linking them to the bomb attacks in the seven southern provinces based on our investigation, although some of them are involved with lese majeste (royal defamation) and arms trafficking," he said.

- Previously unknown group -

Instead he described them as a splinter faction of the anti-junta Red Shirt movement loyal to ousted Thai premier Thaksin Shinawatra, who was toppled by the military in 2006.

He said the network called itself the Revolutionary Front of Democracy party -- a previously unheard of group.

A police statement handed to reporters listing the suspects' details said the group aimed to "accumulate arms... and overthrow the government" but made no reference to last week's bomb attacks.

The statement said they currently face one charge of breaching the junta's ban on political gatherings and another of belonging to an unlawful secret society.

Thailand's deputy junta leader General Prawit Wongsuwan was later asked by reporters whether the group had links to last week's attack. He replied with a one word: "No".

No arrests have been made for people directly responsible for the blasts. However one arrest warrant for a wanted suspect has been issued.

Deputy police spokesman Krissana Pattanacharoen on Friday named the suspect as Ahama Lengha from southern Narathiwat province.

"It's clear that he is involved in that incident," he said.

The name is Muslim and Narathiwat is one of Thailand's three southernmost Muslim majority provinces where a local but brutal insurgency has raged for years.

- Murky motives -

Police and the military have ruled out international terrorism for last week's attacks, saying the perpetrators were "local saboteurs".

A number of analysts say the most likely culprits are ethnic Malay militants from the deep south.

The attacks bore many hallmarks of the southern insurgents -- who never claim their operations -- including coordinated multiple strikes and the type of devices used.

But the junta leadership has been adamant that the deep south conflict has not spread north. Instead their focus has centred on domestic political groups who are opposed to their rule.

The Red Shirts have denied any involvement and accused the junta of using the bombs as an excuse to further crack down on opponents.

Thailand's police and military have a history of rivalry. Since the coup, the military have often led national security investigations before handing the task of charging over to police.

Previous bomb probes -- including an attack on a Bangkok shrine last year that killed 20 -- have been marred by confusion and conflicting statements from the authorities.

Paul Chambers, a Thailand-based expert on the military, said police and the military "seem to be at cross-purposes regarding this investigation".

He said that while police were "steadfastly looking for evidence, the military appears quick to presume the guilt" and links to the Red Shirts.