Indonesian police say suspect arrested earlier this week was making explosives more powerful than those used in the 2002 Bali bombings that killed 202 people.
Rikwanto, national police spokesman, said on Saturday that Rio Priatna Wibawa, 23, was linked to Bahrun Naim, an Indonesian national fighting with the Islamic State of Iraq and the Levant (ISIL, also know as ISIS) group in Syria.
Bahrun Naim is believed to have inspired attacks at home, including a January attack in the capital, Jakarta, that killed eight people.
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Rikwanto, who goes by one name, said bomb-making explosives were recovered from a laboratory in Wibawa's home in Majalengka, a town in West Java province.
Wibawa was making bombs three times as powerful as the Bali bombs, Rikwanto said.
A security crackdown since the 2002 Bali bombings, carried out by the al-Qaeda-linked Jemaah Islamiyah, netted hundreds of its members and reduced their capacity for large attacks.
But a new threat has emerged, from the hundreds of Indonesians who have travelled abroad to fight for ISIL and from their supporters in Indonesia.
Rikwanto said Wibawa, a dropout from an agricultural university who is believed to have been influenced by the writings of Aman Abdurahman, a religious leader, received funds from Indonesians working in Saudi Arabia, Malaysia and Taiwan, and was operating under the direction of Bahrun Naim.
Several other suspects were believed to be involved in the bomb-making and police are searching for them, Rikwanto said.
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The police, from their interrogation of Wibawa, believe he obtained bomb-making materials from contacts in Java, Sumatra and East Nusa Tenggara in Indonesia, as well as the Philippines.
Possible targets for attacks were parliament building, police headquarters, the Myanmar embassy, television stations, places of worship and cafes, according to Rikwanto.
Chemicals seized from Wibawa's laboratory included cyclotrimethylenetrinitramine (commonly known as RDX) - a component in plastic explosives, TNT, a high explosive peroxide - hexamethylene triperoxide diamine (known as HMTD), and gunpowder.
Source: News Agencies