Authorities in New Delhi have launched a special investigation into a fire that gutted a Catholic church in an area that protesters claim was a targeted attack against Christians.

More than 5,000 Christians picketed the Delhi Police Headquarters over two days after the fire broke out at the Saint Sebastian Catholic Church on December 1.

The protesters demanded more police action after the delayed response of authorities stoked fears the attack could have been launched by members of the community.

As well as providing security in other churches in the capital, the police heeded protestors' demands that they expedite the probe into the cause of the fire.

Suspects would be quickly identified if they emerge, said Deepak Mishra, additional commissioner of police for law and order.

Kapil Kumar, another investigating police officer, said the investigators have ruled out communal attack as a possible motive in the fire.

"Everything will come out in the open once the investigation is complete. The area is totally calm. There is no fear of any communal tension in the area," he told ucanews.com.

The fire damaged the church's interior and destroyed the altar. No one was reported injured at the time of the incident.

Police investigators initially looked into an electrical short circuit as the cause of the fire, but the parish priest of Saint Sebastian, as well as other laypeople disputed the initial finding.

Father Anthony Francis, parish priest of Saint Sebastian, said he noticed kerosene in water puddles after the fire, leading him to suspect that the blaze might have been started intentionally.

"Kerosene was used for the fire, as it formed a layer on the water used by the fire brigade to douse the flames. The forensic department has taken samples of the water for analysis," he said.

The priest said investigators found kerosene bottles on the first floor of the church.

Francis insisted the church's electrical wiring had been working well.

Father Savari Muthu Sankar, spokesman for the Delhi archdiocese, said the church sent a delegation to meet with the governor of New Delhi to press for an impartial and speedy investigation into the case.

Copies of the appeal were sent to Prime Minister Narendra Modi and federal Home Minister Rajnath Singh.