The region (India and Sri lanka) is 90% Tamelese . It's a blend of all those religions. The India part of it is majority Hindu, So you'd be correct that way. But we are talking about Sri Lanka, which although a sliver of the continent, doesn't share such a large majority of Hindu, but rather a more equal blend of Muslim, Siekh, and hindu.
As I mentioned, this rebel group is made up of kidnapped children from all of those, whatever they can grab from the local villages in the area.
It's not a Islamic cause they are fighting about, it's a Tamelese independance one, hence the name, Tamel Tigers
The LTTE are nominally Hindu...but mostly atheist-leaning. Theirs is not a religious war. They are ethnic Tamils, distinct from the Sinhala majority of Sri Lanka. Major bloody riots in the early 80s spurred the LTTE movement. They are somewhat akin to the IRA. Even the conflict bears resemblance to the conflict in Ireland.
India has long designated the LTTE as a terrorist organisation.