Indonesian police said they have arrested at least five militants with sympathies for the Islamic State in Iraq and Syria (ISIS) terror group, and confiscated chemicals and weapons being readied for attacks on the Shi'ite community, and during the Christmas and New Year celebrations.
The men were arrested last Friday and Saturday in Central Java and West Java provinces, with police saying they found a map of Greater Jakarta in a raid and a man groomed to be a suicide bomber.
The arrests were carried out following intelligence tip-offs from the US Federal Bureau of Investigation and the Australian federal police, media reports said.
Police seized in the raid a manual on bombmaking, a laptop and books on militancy. Also uncovered were a nine-volt battery, two pieces of pipe, wires, nails, urea fertiliser and ball bearings - ingredients often used by terrorists to make bombs.
The Sydney Morning Herald newspaper, quoting the Australian police, said nine militants were nabbed in five Java cities.
The would-be suicide bomber, Zaenal, 35, is from Sulawesi and had for the past six months stayed at an Islamic boarding school in Tasikmalaya, West Java province. A fellow militant, Asep Urip, 31, was working there as a teacher.
Both were arrested last Friday when they were riding a motorcycle in Tasikmalaya. Police found an ISIS flag in a raid on Asep's house.
Earlier that day, police had arrested two others, Iwan alias Koki, and an unidentified man who was with him. The duo had previously stayed at the Al Mubarok Atturmudzi Islamic boarding school with Zaenal.
The fifth man, Abu Jundi, was arrested in Sukoharjo in Central Java last Saturday. A raid on his rented house yielded bombmaking material and a Greater Jakarta map.
Chemicals and weapons were found buried under a tree at one raid site in the city of Solo.
The Jakarta Globe newspaper said the militants planned to launch attacks in Java and neighbouring Sumatra on communities of Shi'ites, who represent a tiny minority in Indonesia.
The arrests came at a sensitive time of the year for Indonesia, with security officials raising the alert level around the Christmas and New Year's Eve periods when militants had been active in the past.
Also, Indonesia's counter-terrorism forces have been on high alert after detecting elements of domestic militants closing in on Jakarta. Officials have also tightened surveillance on citizens recently deported to Indonesia after trying to link up with ISIS by entering Syria via Turkey.
The authorities plan to deploy more than 150,000 security personnel and several religious organisations to safeguard 33,800 churches and other public places during Christmas and New Year's Eve celebrations, the country's military chief said last Friday.
Indonesia's weak security laws have prevented the authorities from arresting people who had gone to Syria to join the militants or had pledged allegiance to ISIS, but efforts are under way to tighten regulations to allow for more preventive measures.
Inspector-General Arief Dharmawan, deputy head of enforcement at Indonesia's National Counter- Terrorism Agency (BNPT), said last month that 162 Indonesians have been deported, mostly from Turkey, as they were about to cross into Syria.
Among them were 40 male adults, classified as men of fighting age, who have since been released back in their home towns.
Mr Adhe Bhakti, a researcher at the Centre for Study of Radicalism and Deradicalisation, said amending the laws on terrorism is urgently needed to curb the increasing influence of ISIS in the country.
Indonesia is also facing a big challenge in monitoring former terrorists who have finished serving jail time. There are today 598 former terrorist inmates in the country and 212 terrorist inmates, according to data from BNPT.
- Additional information from Agence France-Presse