Thailand's government declared a state of emergency in Bangkok on Sunday after arresting a leader of protests that forced the cancellation of an ASEAN summit the day before. Prime Minister Vejjajiva Abhisit said the government took the decision because the problems threatening stability were escalating. "The government has to declare the state of emergency to restore normality as soon as possible," Abhisit said.

Authorities arrested anti-government protest organiser Arisamun Pongruengrong, who had led a mob to disrupt a summit of the Association of South-East Asian Nations (ASEAN) and its dialogue partners in the seaside resort of Pattaya, 100 km south of Bangkok.

The arrest provoked fury from Arisamun's followers, who began to converge on key government buildings and block traffic in the capital city.

Abhisit and his Democrat party government were widely criticised in the local media Sunday for failure to stop the protestors from disrupting the ASEAN summit.