The 16-count indictment, issued by federal prosecutors Thursday, accuses Rahmat Abdhir, a U.S. citizen who lives in northern California, of sending cash, rifle scopes and two-way radios to his brother, Zulkifli Abdhir, in the Philippines.
Zulkifli is an alleged bomb-maker for Jemaah Islamiya -- an al-Qaida-linked terrorist group operating in Southeast Asia.
Zulkifli is said by the U.S. government to be a member of Jemaah Islamiya's central command, which would make him one of the most senior members of the group still alive and at large. The indictment says he may have used the radios to make bombs.
The indictment also reproduces excerpts from dozens of e-mail exchanges between the brothers, in which Zulkifli describes living with, fighting alongside and teaching sniping skills to fighters from the Moro Island Liberation Front, an insurgent group fighting the Philippines government on the southern island of Mindanao.
The exchanges are significant, because they lend weight to charges -- long-denied by the MILF -- that the group is providing sanctuary to al-Qaida-linked militants.