Indonesian counter-terrorism police said on Sunday they had arrested suspected Islamist militants in locations across the island of Java, foiling separate plots to bomb minority Shia communities and target Christmas and New Year celebrations.
Bomb-making materials and 'jihad manuals' were seized after the arrest of six men in central and west Java who were either members or supporters of the Sunni militant group Islamic State, the Jakarta Globe daily said on its website.
Chemicals and weapons were found buried under a tree at one raid site in the city of Solo.
National Police Chief General Badrodin Haiti told the Globe that the raids to round up the men, which began on Friday, were prompted by intelligence from the U.S. Federal Bureau of Investigation and the Australian Federal Police.
The Globe said their plan was to launch attacks in Java and neighbouring Sumatra on communities of Shia, who represent a tiny minority in Indonesia.
Indonesia has the world's largest Muslim population, the vast majority of whom practise a moderate form of the religion.
Separately, police said four men suspected of being weapons specialists and strategists of the al Qaeda-affiliated Jamaah Islamiah group had been arrested in east Java.
"They had made plans for actions in the near term, in relation to Christmas and New Year," Budhi Herdi Susianto, chief of police in the east Java regency of Mojokerto told Metro TV.
He gave no details of their plans.
News agency AFP reported that, according to arrest documents, they were planning a suicide bombing in Jakarta, the country's capital, during New Year celebrations.
A police source said that, in all, there were "interlinked" arrests in five cities across Java.
The Globe said that in one raid, police had seized bomb-making material, including detonators, lengths of piping, nails and buckshot, and various chemicals. They also found a book on waging jihad and a map of the Greater Jakarta area.
Fears of militant resurgence
Indonesia saw a spate of militant attacks in the 2000s, the deadliest of which was a nightclub bombing on the holiday island of Bali that killed 202 people, most of them tourists.
Police have been largely successful in destroying domestic militant cells since then, but officials now worry about a resurgence in militancy inspired by groups such as Islamic State and Indonesians who return after fighting with the group.
Authorities plan to deploy more than 150,000 security personnel and several religious organisations to safeguard churches and public places around the country during Christmas and New Year's Eve celebrations, the country's military chief said on Friday.
Security and surveillance had already been stepped up in some areas following the attacks in Paris last month that killed 130 people and for which Islamic State has claimed responsibility.
Indonesia is home to an estimated 25 million Christian people, roughly 10 percent of the total population. They live mostly not on smaller, more remote islands, not on the two most populated islands of Java and Sumatra.