Olivia Rondonuwu, Jakarta – Opulent Christmas decorations at shopping malls in Indonesia, the world's most populous Muslim nation, could incite anger among non-Christians, the country's highest Islamic authority said on Thursday.

Although 90 percent of the country's 240 million people are Muslim, the capital's myriad glitzy malls have been decorated with Christmas lights and bunting – including faux snow, Santas and nativity scenes. A man hold a candle during a Christmas mass at the Gelora Bung Karno stadium in Jakarta December 11, 2010. (REUTERS/Supri/Files)

"Christmas describes a certain religion, and if the religion advertises it too overtly – even though they have only a small number of followers – it will cause jealousy and anger from other groups," said Ma'ruf Amin, of Indonesia's Ulema Council.

Retailers say the giant Christmas trees, paper mache reindeers and carols serve no religious purpose and are there to attract more shoppers during the holiday seasons. But Amin said over-the-top festivities could hurt existing tolerance.

"You can attract buyers without using religious symbols," he told Reuters. "Even the majority (Muslims) celebrate their big days modestly. How come a few followers who have plenty of money celebrate it the other way?"

Indonesia's Muslims are overwhelmingly moderate, but analysts say hardliners are becoming increasingly vocal, creating tensions that if not managed, could spark the sort of religious violence last seen over a decade ago.

The Jakarta Post quoted a pluralist group, The Wahid Institute, recording 133 challenges to religious freedom this year, saying the attacks were directed at Christians and Ahmadiyya followers, an Islamic sect considered heretical by some.

A different group, The Moderate Muslim Society, told the newspaper it recorded 81 cases of religious intolerance this year compared to 59 cases in 2009 – most also against Christians or Ahmadiyyas.

Debate between moderates and Islamists is growing on social media sites such as Twitter and Facebook, and topics range from whether Muslims can even greet Christians by saying "Merry Christmas", to the establishment of new places of worship and religious symbols.

Officially secular, Indonesia nevertheless marks Friday as a Christmas public holiday.