By Rachel Harvey BBC correspondent in Jakarta

The Bali bombings may represent a shift in strategy by the Islamic group Jemaah Islamiah (JI) in response to the United States-led war on terror, says a Brussels-based think-tank.

Splits may have emerged in the organisation's leadership with younger members seeking a more aggressive approach, concludes an International Crisis Group (ICG) report detailing Jemaah Islamiah's Indonesian operations.

JI is widely believed to have been behind a series of attacks in south east Asia, including bomb explosions across Indonesia on Christmas Eve two years ago.

Those attacks were assumed to be revenge for violence carried out by Christians against Muslims during conflicts in the Moluccan Islands and Sulawesi.

Westerners targeted

But Jemaah Islamiah has also been implicated in the Bali bombings in which the victims were mostly foreign tourists.

In its report, ICG says the US led war on terror has replaced local issues as the main focus of Jemaah Islamiah's operations.

Abu Bakar Ba'asyir's leadership may be split

The targets now are westerners rather than Indonesian Christians.

The author of the report, Sidney Jones, says that represents a split in the leadership of Jemaah Islamiyah.

Its alleged spiritual leader, Abu Bakar Ba'asyir, now in custody in Indonesia, is being sidelined by a younger, more militant wing.

Mr Ba'asyir, apparently after 11 September, warned it could be counter productive to engage in these kinds of attacks and was therefore at odds with radicals who were doing just the opposite.

The report also details the way that family connections and old school ties are being used by the group to attract recruits.

That certainly fits the pattern emerging from the police investigation into the Bali bombings.

At least three brothers have been arrested and almost all the alleged suspects attended one of two Islamic boarding schools in Java.

ICG is calling for more resources to allow Indonesia to investigate the Jemaah Islamiah network more thoroughly.