Senior figures in the Students' Islamic Movement of India conducted at least three secret combat camps last year, police and intelligence agencies investigating them said Wednesday.

They said new recruits were given basic training in jungle-craft, elementary marksmanship with air-rifles and the principles of bomb-making. According to the investigators, Mohammad Subhan, the principal instructor at the camps, is SIMI's main bomb-maker and has links to the perpetrators of the 2003 Mumbai terror strike.

Police and security personnel arrested 13 top leaders of SIMI in Indore in the central Madhya Pradesh state early this week.

Investigators said the first of these camps was held in the third week of April 2007 near Hubli in Karnataka. SIMI's south India chief, Hafiz Hussein, and Shibli Peedical Abdul organized the camps.

Abdul is alleged to have links with the Lashkar-e-Toiba terror cell that carried out the 2006 serial bombings in Mumbai.

Hussein, operating under the code name Adnan, had supervised a large-scale expansion of SIMI's network in Karnataka state, investigators say. A resident of Bijapur in the same state, Hussein ran a network of religious front organizations through which SIMI recruited extremists.

Abdul, who worked as a computer engineer with a multinational company in Bangalore, was among his key lieutenants.