Officials in Jakarta denied that Indonesian militants might be among Islamic insurgents fighting US forces in Iraq.

The denial came amid reports that jihadist texts written in Indonesian have been uncovered by US Marines fighting in the rebel stronghold of Fallujah.

Marine forces fighting around Fallujah's al-Kabir mosque – an insurgent flashpoint – found Indonesian books calling for holy war when they stormed the building to end sniper attacks.

While the militants had already fled into the warren of nearby alleys, the texts and other books from Pakistan were found strewn on the floor along with abandoned AK-47 rifles and grenade launchers, Newsweek magazine reported.

Indonesia's chief foreign spokesman Marty Natalegawa denied the Marines' discovery meant Indonesian fighters were among the ranks of anti-coalition insurgents.

"There is no way to confirm they are there, but there have not been any reports to us," he told AAP. "We need to see something more factual and we need to see something concrete.

"I don't accept there are any there." But western security experts and diplomats in Jakarta are privately concerned Indonesian jihadists may have joined foreign fighters in Iraq.

"The fear is that these people will come home again one day and provide a fresh hard-core for groups like Jemaah Islamiah," one senior western envoy said.

"Afghanistan has already served as a training ground. Iraq may be shaping as another." Militant Muslims from South-East Asia trained in al-Qaeda camps in Afghanistan before a US-led campaign ousted the nation's hardline Taliban rulers.

Key Bali bombers Imam Samudra, Mukhlas and Amrozi were placed on the path to terrorism while fighting the Soviet occupation during the mid-1980s.

In Afghanistan they met several of al-Qaeda's leaders, as well as fellow Indonesian Riduan Isamudin, better known as Hambali, who served as JI's operations commander before his capture last August in Thailand.

But Natalegawa said the only Indonesians believed to be in Iraq now were a group of thirty students and a handful of women married to Iraqis.

Two Indonesian women were taken hostage and later released by Iraqi militants in October amid demands radical cleric and alleged JI spiritual leader Abu Bakar Bashir be freed.

Bashir is on trial in Jakarta over charges linking him to several terrorist attacks, including last year's attack on the JW Marriott Hotel in Jakarta.

In August an Indonesian and two Iraqis were killed when their convoy was ambushed in the northern Iraqi city of Mosul.