The Islamic Defenders Front (FPI) - the vigilante group that spearheaded three mass protests in Jakarta calling for the city's Christian governor to be jailed for alleged blasphemy - were guarded by police when they went to seven shopping centres in Surabaya on Sunday.

The hardline group told managers at the centres of a fatwa issued by Indonesia's top Muslim scholarly body, the Majelis Ulema Indonesia (MUI), banning Muslims from wearing Christmas apparel such as Santa hats.

But police have been criticised by Indonesia's largest Islamic civil organisation, Nahdlatul Ulama (NU), and human rights groups for providing security at the shopping centre visits, which some say gives legitimacy to radical fringe groups.

National Police spokesman Rikwanto said Surabaya police had persuaded the FPI to restrict numbers to 35 rather than the hundreds planned and to explain the fatwa outside the seven malls rather than going inside.

"We did not provide an escort to them, we safeguarded their action so it wouldn't go wild beyond their original plan of promoting the MUI edict," he told Fairfax Media.

But NU Supreme Council General Secretary Yahya Cholil Staquf said the fatwa was not legally binding and he did not understand why police guarded the FPI when they carried out "anarchic actions".

"The police keep doing this over and over," Mr Yahya told Fairfax Media.

Earlier this month the Islamic Group Ahlus Sunnah Defenders (PAS) forced the closure of a Christmas service in Bandung, West Java, claiming it was illegal to hold a religious service outside a designated place of worship and the participants lacked a permit.

Both claims have been refuted.

Mr Yahya said the Islamic group's actions in Bandung were unlawful but instead of enforcing the law, police brokered a mediation between the Ahlus Sunnah Defenders and the church organisers, which ended in the event being closed.

"This is absurd … the police never act to enforce the law," he said. "They are helping radical groups to force the minorities to comply with whatever the radicals want."

Mr Yahya said the Christmas costume controversy was "actually meaningless". "It's been happening all the time that shop workers in malls wear Christmas costumes. People just keep shopping - they don't care that much."

The Jakarta-based Setara Institute for Peace and Democracy said providing the FPI with an escort in Surabaya was a blunder on the part of police that weakened the supremacy of the law of Indonesia.

"The police should actually have prevented and banned the intimidation," the Setara Institute said in a statement.

Grand City Mall marketing manager Yudhi Saharudin said the FPI saw for themselves when they visited on Sunday that Grand City Mall did not have any staff wearing Christmas costumes.
 
"We did not have anything they complained about. We only have decorations. We have some big Christmas trees at the entrance and at other locations at the mall. And it seems that they don't have a problem with them."

The thuggish FPI, which wants to see a rigid interpretation of Islamic practice implemented in Indonesia, is notorious for attacking religious minorities and conducting sweeps of bars during the Islamic fasting month of Ramadan.

Last year the FPI also visited Surabaya shopping centres - where many of the store owners are ethnically Chinese - to ensure Muslim employees were not being forced to don Christmas apparel.

But many believe the group has been emboldened by the sheer number of protesters at rallies calling for the imprisonment of Jakarta governor Basuki Tjahaja Purnama, known as Ahok.

The third rally, on December 2, attracted an estimated 500,000 to 600,000 people.

"The fact they got (President) Jokowi to come and pray with them at the second rally is also a huge sign of their clout," says Tim Lindsey, the Director of the Centre for Indonesian Law, Islam and Society at Melbourne University.

Ahok's court case for allegedly insulting Islam has been expedited, with the second day of the trial to be held on December 20.

But religious intolerance and anti-Chinese sentiment continues to simmer in Indonesia. About 1 to 4 per cent of Indonesia's 250 million people are ethnically Chinese, the majority of whom are also Christian.

Their relative affluence has fomented resentment for centuries in Indonesia.

A street banner in Magelang in Central Java this month urged people to fight Chinese and foreign imperialism and only support indigenous Indonesian shops.

with Karuni Rompies