Religious intolerance is on the rise in Indonesia, as shown by attacks on a minority Muslim sect, a Catholic priest and a moderate Muslim leader said on Wednesday.

The tolerant image of Muslim-majority Indonesia has been knocked in recent months as mosques and buildings belonging to Ahmadiyya, a sect branded by many Muslims as "heretical", have come under attack amid a debate over whether to outlaw the group.

Christians and other minority religions have in general been able to worship freely in Indonesia, with few problems for example over changing religion or inter-religious marriages, Catholic priest Franz Magnis told foreign correspondents.

"This is a situation you don't have in many other countries with Muslim majorities, but tolerance is now under attack," said Magnis, a German-born Jesuit priest and long-term resident.

"For Christians, attacks against churches, very often against churches which did not have the full set of permits, began to increase enormously since 1990," he said.

The state had a responsibility to protect minorities but police often failed to deal with religiously motivated aggressive crowds, he added.

"In general, religious freedom is still a fact, but it is also a fact that our state is a weak state and doesn't dare to enforce the law if state people think that it is against religious feelings of the majority," he added.

He noted that the state had failed to take strong action against militants blamed for a series of bomb attacks, including a series of blasts at churches in 2000 that killed 19 people.

But after militant group Jemaah Islamiah attacked nightclubs in Bali in 2002, killing over 200 people, the authorities acted.

"To my great astonishment within six weeks (of the Bali bomb) they caught the terrorists," he added.

"But of the 30 bombs that exploded on Christmas night in the year 2000 they caught nobody except a few people when the bomb exploded before it was brought there," he added.

The authorities were slow to act on other occasions, he said, referring to a rally on June 1 when the Islamic Defenders' Front (FPI), a militant group, beat up women and elderly people who had gathered to celebrate freedom of religion and tolerance for Ahmadiyya.

"This case of last Sunday (June 1) is maybe a blessing in disguise because it was such a brutal thing, such a stupid brutal thing, that it outraged many people," he said.

Zuhairi Misrawi, executive director of the Moderate Muslim Society, speaking on the same panel, said that a survey showed young Indonesians still had strong support for Pancasila, Indonesia's official ideology that stresses religious tolerance and unity.

But he said moderate Muslims were concerned over the growth of radical groups and needed to respond and ensure that the rights of minorities were protected.

"We are afraid that in future the radical groups will ban the activities of Christians," he said.