Thailand's military has filed a sedition case with police against a group of opposition politicians and academics, accusing them of stirring unrest with talk of amending the constitution, police said on Friday.
Police in Thailand's restive deep south are looking into the complaint, which was raised by a unit of the military that operates in the area.
"We're investigating whether wrongdoing had been committed and by whom," police spokesman Kissana Phathanacharoen told Reuters.
Thailand's sedition law is broadly worded, and some rights activists say it has been increasingly used against political opponents of the government since a coup in 2014.
The complaint came after 12 prominent opposition leaders, politicians, and academics held a public seminar last week in the country's southern province of Pattani about amending the 2017 constitution written by allies of the military.
The Pheu Thai party, which leads the opposition, denied that the seminar stirred any unrest, adding that opposition parties would file a counter-complaint against the military for reporting falsehood.
Under Thai law, when a complaint is filed, police must investigate and decide whether there are grounds to pursue criminal charges.
The opposition also called the case another effort to harass them after a messy March election that formally installed coup leader Prayuth Chan-ocha as prime minister.
Amending the charter, passed under the military junta that seized power in 2014, is a common goal for seven opposition parties. The seminar was the latest in a series of public hearing sessions the opposition parties aimed to hold in every region on the issue.
The seminar also addressed issues specific to the Muslim-majority south, including religious tensions in the mostly Buddhist country, and how the constitution could be amended to solve them.
An ongoing insurgency has dragged on since 2004 in the southern border provinces of Pattani, Yala, Narathiwat, which were part of an independent Malay Muslim sultanate before Thailand annexed them in 1909.
Piyabutr Saengkanokkul, secretary-general of opposition Future Forward Party, said the sedition accusation was the military resorting to the "same old tactic" to silence political opponents.
"We, the opposition parties, will push ahead to amend the constitution," he said in a news conference