BANGKOK - Two high-ranking Thai police officers have been arrested for royal defamation, an official said Sunday, a rare charge against senior public servants as lese majeste cases mount following a May coup.

Central Investigation Bureau chief Pongpat Chayapun and his deputy Kowit Vongrongrot have been charged under the strict lese majeste law, a police spokesman told AFP.

Under the law, which is Section 112 of the Thai criminal code, anyone convicted of insulting the king, queen, heir or regent faces up to 15 years in prison on each count.

“The two police officers have been arrested and charged under Section 112,” national police spokesman Prawut Thavornsiri said, confirming their names and positions.

He would not confirm where they were being held or give any other details of the arrests.

Rights groups say there has been a rise in both charges and convictions under Thailand’s royal slur law - one of the strictest in the world - since the army seized power on May 22.

Under martial law - declared two days before the coup by then-army chief Prayut Chan-O-Cha, who is now premier - suspects are now tried under military courts, where there is no right to appeal. Earlier cases were handled in civilian courts.

The royal family is a highly sensitive topic in the politically turbulent kingdom where 86-year-old King Bhumibol Adulyadej, the world’s longest reigning monarch who is currently in a Bangkok hospital, is revered by many as a demi-god.

The law is designed to protect the monarchy from insult, but academics say it has been politicised in recent years as the king’s reign enters its twilight.

Many of those charged have been linked to the “Red Shirt” movement, whose activists are broadly supportive of fugitive former premier Thaksin Shinawatra.

It is rare for high-ranking public servants to face charges under the law.

Last week a Thai radio show host was sentenced by a military court to five years in jail for royal defamation.

Early in November a 24-year-old student was jailed for two-and-a-half years for defaming the monarchy.

And in another recent case a 28-year-old musician was sentenced to 15 years in jail for writing insulting Facebook posts about the royals between 2010 and 2011.

The coup was the latest twist in Thailand’s long-running political conflict, which broadly pits a Bangkok-based middle class and royalist elite, backed by parts of the military and judiciary, against rural and working-class voters loyal to Thaksin.

On Sunday afternoon two government ministers, accompanied by Prayut, were sworn in before the king at Bangkok’s Siriraj hospital, the Royal Household Bureau said in a statement.

The ceremony took place two days after it was scheduled as the palace Friday said the king’s medical team had advised against him granting an audience.

The health of the elderly monarch, who has suffered from a series of ailments in recent years, is a matter of public concern in Thailand.

In early October Bhumibol was rushed to hospital where he underwent an operation to remove his gall bladder and has remained admitted since.