Muslim students demonstrate against the 'ninja' murders

The angry mob attacked shops, banks and vehicles. Police fired warning shots to fend off the stone-throwing crowd, and reinforcements had to be sent in to restore calm. Two people were reported injured.

The suspect, Ahmad Sulaiman, was arrested by police on Saturday, near the town of Pasuruan, for allegedly being involved in the ninja-style murders of black magicians and Muslim clerics.

In the past two months more than 150 people -many of them Muslim - have died in the attacks, which have been carried out by assailants dressed in black and wearing masks, similar to so-called ninjas.

Vigilante patrols

Local communities have set up vigilante patrols, and on learning about the arrest at the weekend, a crowd gathered outside the house of the local police chief, demanding in vain the hand-over of the suspect.

"The man is still being held here and we have also arrested four of the rioters for questioning," said an officer at the Pasuruan police headquarters.

On Monday Muslim students staged a demonstration in front of Parliament in Jakarta, against the government's inability to put an end to the killings.

Upset by the ninja attacks, vigilante groups have been capturing and attacking people found without identity documents or roaming the countryside after dark.

In Central Java crowds beat to death three people suspected of belonging to the Ninja groups, the Media Indonesia daily said.

In Malang, mobs last week killed eight people, beheading at least two of them and burning another.

The BBC Indonesia correspondent, David Willis, says there is suspicion in Jakarta that politicians may have stage-managed the violence to destabilise the politically-important province ahead of next year's parliamentary elections.