Experts say a Southeast Asian terrorism network has expanded its influence in Central Sulawesi amid escalating violence during the past month.

A new report from the International Crisis Group says terrorist cells are behind attacks against Christians in central Sulawesi during the past three years.

Those attacks were previously thought to be an extension of local sectarian violence between Muslims and Christians that has plagued the area since 2001. But research by the Brussels-based policy institute shows that the attacks were engineered by the regional terror network, Jemaah Islamiah, as part of its agenda to escalate religious conflict.

Jemaah Islamiah is connected to bombings in Indonesia, including blasts in Bali in 2002 that killed 202 people.

Members of an Indonesian anti-terror squad take part in a raid on an Islamic militant stronghold in Poso, 22 Jan 2007

"The problem now is, and it is a real serious danger, is that the jihad in the Poso area that has up till now been primarily focused on revenge against local Christians will in fact turn into a jihad against the police, and that is what needs to be avoided at all costs," said Jones.

A January 11 raid on militant hideouts in Central Sulawesi province caused an influx of mujahedin fighters to help defend remaining members of Jemaah Islamiah. Fifteen people were killed in a three-hour shootout on Monday in Poso, the provincial capital.

The raids were aimed at capturing 20 key militant leaders placed on a most wanted list in May 2006.

In the report, Sidney Jones calls for the Indonesian government to move quickly to calm rising tensions. She questions whether police used excessive force in the raid on Monday.

"Well I think the government has to move extremely quickly to both explain why these individuals were wanted, exactly what they had done, but then I also think it is important that they investigate the way the operations were conducted so that the anger against the police is at least addressed and people can see through an independent investigation whether additional measures could have been taken to prevent these casualties or not," said Jones.

Central Sulawesi remains scarred by sectarian conflicts between Muslims and Christians that have killed more than 1,000 people since 2001.

Most Indonesians are Muslim, but about half of the population in Poso is Christian.