The suspect, arrested at his home in Majalengka regency in West Java earlier this week, was identified as Rio Priatna Wibawa, 23, who is believed to be a member of an Indonesian group that supports Islamic State.
Local media reported that the amount of explosives seized would have resulted in a blast twice as powerful as the bomb that killed 202 people in a Bali nightclub in 2002.
Police also confiscated some books, a black flag, rounds of bullets and several weapons, including an air rifle and a machete, police spokesman Boy Rafli Amar told a press conference on Saturday.
"We are now trying to prove how he had planned everything, whether he was working alone and how he managed to get the money to buy that much explosive material," he said.
Wibawa, who studied agricultural science at university and was unemployed, was a self-taught bomb-maker who had planned to distribute explosives to several places across Indonesia, Amar said.
Indonesia has seen a string of Islamic State-linked attacks this year, the biggest of which was a gun and bomb assault in the capital Jakarta that killed four people in January.
Authorities are concerned about a resurgence in radicalism and say there are hundreds of Islamic State sympathizers in Indonesia, home to the biggest Muslim population in the world.
Lately, anger has been mounting in the Muslim-majority nations in Southeast Asia, such as Indonesia and Malaysia, over a crackdown on Rohingya Muslims in Myanmar, leading to demonstrations in several cities, including Jakarta.
Separately, police have also detained 9 suspected Islamic State sympathizers from a different group, who police said had incited violence at a mass protest on Nov. 4 by Muslims calling for the removal of Jakarta's Christian governor, who is accused of insulting the Koran.
International / ASEAN/Philippines
Indonesia arrests militant planning bomb strike on Myanmar embassy
Indonesian police show items recently seized, including weapons and bomb-making materials, that they say were intended for use to attack government buildings and the Myanmar embassy, at police headquarters in Jakarta.
Police in Indonesia have arrested a suspected Islamist militant and seized a large quantity of bomb making material that he planned to use in attacks on government buildings and the Myanmar embassy in Jakarta next month, a police spokesman said.
