Indonesia's Supreme Court has rejected an appeal by a woman whose complaint about the volume of mosque loudspeakers led to an 18-month prison sentence for blasphemy.

Key points: Meliana's case is the latest in a string of high-profile blasphemy cases targeting minorities

Meliana's case is the latest in a string of high-profile blasphemy cases targeting minorities Indonesian law criminalises insulting any of its six official religions

Indonesian law criminalises insulting any of its six official religions The country's largest Muslim organisation and other religious groups have called for Meliana's release

In a March 27 ruling posted on the court's website on Monday, the court rejected the appeal by Meliana, a 44-year-old ethnic Chinese, Buddhist resident from the island of Sumatra.

The court did not provide a reason for the decision.

Meliana's lawyers said she had made remarks in a private conversation in 2016 on the volume of mosque loudspeakers. Those remarks were twisted to appear like she was objecting to the call to prayer itself and repeated in the community and on social media, her legal team said.

"This is another nail in the coffin of religious freedom and tolerance in Indonesia because of institutionalised discrimination," Andreas Harsono of Human Rights Watch said.

Meliana, a mother of four, is serving an 18-month sentence in a prison in Medan, Sumatra.

Senior members of Nahdlatul Ulama, the country's largest Muslim organisation, have said her remarks should not be considered blasphemy.

Human rights and interfaith groups have rallied for Meliana's release, arguing that she merely expressed her opinion peacefully.

Indonesia has the world's largest population of Muslims, and sizeable communities of Buddhists, Christians and other religious minorities.

Criticism, hostility or practicing "deviant" interpretations of any of Indonesia's six official religions has been illegal since 1965, however prosecutions had been rare until the past decade.

In 2017, Jakarta's Christian then-governor Basuki "Ahok" Tjahaja Purnama was jailed for two years for allegedly insulting the Koran.

Wires/ABC