A top Indonesian antiterror official said on Wednesday that regional militant group Jemaah Islamiyah was behind a series of 'book bombs' in Jakarta, one of which injured four people.

The first bomb, hidden in a hollowed-out thick book, exploded on Tuesday afternoon as police attempted to defuse it.

The package was addressed to Ulil Abshar Abdalla, a well-known liberal Muslim figure who espouses pluralism and religious tolerance. It came with a threatening letter urging Abdalla to write a preface to the book which was entitled 'They Deserved to be Killed: Because of their Sins to Islam and Muslims.'

National Anti-Terror Agency (BNPT) chief Ansyaad Mbai told AFP: 'It's the work of terror group Jemaah Islamiyah (JI) which has been actively launching bomb attacks in this country.'

JI is a South-east Asian extremist group inspired by Al-Qaeda, which carries out terror attacks to destablise governments in a bid to unite the region into a fundamentalist Islamic state.