The suspects were arrested on the island of Sumatra in late June and early July. Police said they had found 20 improvised bombs and a safe house in Palembang, South Sumatra, containing 18 computer hard drives.

They had planned to bomb a backpacker cafe in the tourist town of Bukittinggi, West Sumatra, prosecutors said in a 150-page charge sheet handed to defence lawyers.

Other charges include planning to cause 'mass casualties' and attack strategic assets, and helping suspected terrorists.

Cell member Mohammad Hasan bin Saynudin, from Singapore, received military training in Afghanistan around 2000 and met Al-Qaeda leader Osama bin Laden, according to the charge sheet.

He was also an accomplice of notorious JI bombmaker Azahari Husin, who was shot dead by police in November 2005.

Azahari was a close associate of Malaysian extremist Noordin Mohammad Top who allegedly masterminded the 2002 Bali bombings and subsequent attacks in Indonesia.

Hasan was also associated with Mas Selamat bin Kastari, the alleged leader of JI's Singapore branch who escaped from prison there in February last year, the prosecutors said.

In addition to the planned cafe attack, the cell had plotted to kill two Christian priests in Jakarta in August 2006 but abandoned the plan after learning they lived too close to a market.

It targeted another priest named Yosua Winardi for 'turning Muslims into apostates,' according to the charge sheet.

Priest Yosua was attacked in October 2006 with a hammer, and was hospitalised for cuts on his head and face. -- AFP