The world's largest Islamic organisation and a separatist group have condemned and blamed Thai authorities for the Narathiwat mosque massacre - while the government has decided to send over a thousand additional forces to the troubled South.

A group of gunmen sprayed rifles into the crowded Al Pukon mosque in Joh I Rong district Monday night, killing 11 Muslims at prayer and injuring a dozen others.

The separatist Patani United Liberation Organisation (Pulo) said a witness claimed to hear clearly the Thai accent of a gunman on a walkie-talkie at the mosque gate - one of three positions where masked gunners sprayed 105 bullets from a range of assault weapons. A Singha beer bottle cap also was found at the scene.

"This shows that the Patani Malays' lives are in danger, especially in the radiant of Thai enclaves heavily armed by Thai authorities, protected and helped by Ranger squads who often terrorise villagers," the Pulo statement said.

Secretary-general of the Organisation of the Islamic Conference (OIC) Ekmeleddin Ihsanoglu, also condemned the armed assault.

"This tragic incident falls within a string of aggressions conducted by armed and organised elements targeting worshippers and venues in southern Thailand, in a bid to terrorise Muslims and restrain them from demanding their legitimate rights," the OIC statement said.

Ihsanoglu called on the Thai government to undertake a probe into the incident, apprehend its perpetrators in order to refer them to justice, and deploy the necessary efforts to protect the lives and property of Muslims in the deep South.

Army chief Anupong Paochinda earlier rejected allegations about the government armed forces, saying they had nothing to do with the massacre.

The authorities have claimed they will apprehend the culprits soon .

Prime Minister Abhisit Vejjajiva called a meeting yesterday at the Government House to study an operational plan for the deep South for the next fiscal year, worth Bt18 billion.

He instructed officials to hunt down the culprits of the mosque attack but insisted they not set up any scapegoats, which would create more troubles, according to an official at the meeting.

Prime Minister's deputy secretary Panitan Wattanayagorn said the government would send an additional 1,440 security volunteers to help maintain law and order in Pattani, Yala, Narathiwat and Songkhla districts. The government would allocate a Bt400 million budget for the volunteers, he said.

The meeting also approved a proposal by the National Economic and Social Development Board to initiate more than 300 development projects for the region, worth Bt54 billion, between 2010-2012, he said.

In fresh violence in the deep South yesterday in Narathiwat, a gun attack killed two vendors and injured one other while driving to sell fresh food in Chanae district. Phongsakorn Amarin and his wife Duangkamol Amarin died instantly in a pickup truck. His mother in law, Yindee Polpakdi was injured.

A drive by shooting also killed Muhammad Ya-ip Salah in Rangae district.

Police believed the two incidents were part of a spate of on-going violence in the predominantly Muslim region which has already left 3,500 people dead since the beginning of 2004.