Jakarta. Counter-terrorism squad Detachment 88 has arrested 12 suspected militants with alleged links to global terror network the Islamic State in separate operations in East Java, the National Police said on Monday.

Police alleged that the group had plotted attacks and even prepared a hideout.

“They have stored weapons and prepared a place to hide after carrying out future attacks,” police spokesman Brig. Gen. Rusdi Hartono said in a news conference at the National Police headquarters in South Jakarta.

“I need to underline that they plotted attacks but anti-terror squad Detachment 88 has prevented them from happening,” he added.

From the group, the elite squad seized a pistol, 50 bullets, eight knives, two swords, three machetes, dozens other sharp weapons and four flags depicting the Islamic State symbol, he said.

The militants were arrested on Friday for their alleged role in several terror attacks in Mojokerto, Malang, Sidoarjo and the East Java capital of Surabaya.

However, police didn’t disclose those attacks in details pending the ongoing investigation.

A source familiar with the investigation said the group was led by former terror convict Usman bin Sef.

“They are members of a terror cell led by Usman bin Sef aka Fahim, who used to be the leader of Jemaah Islamiyah group in East Java,” the source told Jakarta Globe’s sister publication Beritasatu.

“He was once convicted for harboring Noordin M Top in the aftermath of the 2003 bombing at JW Marriott Hotel.”

The officer, who asked to remain anonymous, was referring to Malaysian-born Noordin, a key figure in shadowy terror network Jemaah Islamiyah blamed for a series of major attacks in Indonesia, including the October 2002 Bali bombings that killed more than 200 people of mostly foreign holidaymakers. 

Known as a bomb expert, Noordin also orchestrated the bombings near the Australian Embassy compound in Jakarta in 2004 and at a Bali restaurant in 2005.

He was killed during a police raid in the Central Java town of Solo in September 2009.

Usman meanwhile was arrested in 2004 on charges of assisting Noordin and concealing information about his whereabouts.

It’s unclear when he was released from prison.