A group of people attacked on Thursday night a church under construction in Harapan Indah residential complex, Bekasi, West Java, leaving several makeshift buildings damaged.
No one was injured in the incident.
The chairwoman of the St. Albertus church construction committee, Christina Maria Rantetana, said the incident happened around 10:45 p.m. on Thursday.
"I saw around 1,000 people dressed in white marching to the church. When they arrived, they started throwing rocks," she told The Jakarta Post on Friday.
"Some of them then entered the church compound and started a fire," she added.
Christina said she immediately reported the incident to the nearest police precinct. Several police officers arrived on the scene within moments but could not calm the mob.
The incident finally ended around midnight after hundreds of Bekasi Police officers arrived.
A motorcycle, a security guard post and at least two makeshift offices were severely damaged in the incident.
Christina said the incident would not alter the church congregation's plan to use the half-finished church to host the upcoming Christmas Eve mass.
"We still plan to use the church for the first time on Christmas Eve," she said.
"After that, we will continue to use the church even though there are no walls and we have to sit in plastic chairs."
Bekasi Police chief Adj. Sr. Comr. Imam Sugianto claimed that the attack was a spontaneous act.
"The crowd gathered to celebrate *the Islamic New Year*," he was quoted as saying by news portal tempointeraktif.com.
"However, when passing by the church, they were suddenly provoked and retaliated," he said.
As of Friday night, Imam said the police had so far detained one suspect for allegedly stealing a drill from the church and questioned other 28 witnesses.
"None of them knew anything and said they had been provoked," he said, obviously believing the attackers.
It was reported last year that several local Islamic organizations had questioned the legality of the church's building permit. The groups alleged the church construction committee had falsified local residents' signatures to obtain the building permit from the local administration.
Christina, however, denied the accusation, saying the committee had completed all administrative procedures to obtain the building permit. The legality of the attack was not questioned.