Fighters often target both Buddhists and Muslims working for the Thai state, including police officers, soldiers, government officials and teachers.
Pattani, together with Narathiwat, Yala and Songkhla, are predominantly-Muslim provinces in Thailand's far south, a region were many residents have long complained of discrimination, especially in education and job opportunities.
Tensions have simmered since the region, formerly an autonomous Malay Muslim sultanate, was annexed by predominantly Buddhist Thailand in the early 1900s.
The provinces see shootings, grenade attacks and car bombings happen almost daily.
The violence has claimed more than 3,900 lives since January 2004, with more than 340 people in 2009 alone.
About 90 per cent of those killed are civilians.
The Thai government has made little progress towards quelling the unrest despite deploying thousands of paramilitary troops - usually residents hired as armed auxiliaries to the regular military - in the area alongside 30,000 army troops.