Chris McCall, Ambon – They are the shock troops of a crusade to defend the Christian faith and they are mostly still at school.

They call themselves "Agas", an abbreviation for "Church Children who Love God". It also means "gnat". Several dozen of them live in the half-finished Catholic cathedral in Ambon, the main city in Indonesia's troubled Maluku Islands, sleeping on the pews without mattresses or sheets.

Give them 220,000 rupiah, however, and they will happily go and make a few bombs for you. Several, with bullet scars on their bodies, grin and smoke as they calmly explain how they make their weapons.

"We are ready to defend the faith of God wherever we have to," says their student commander, Tommi Maurits, 23. "Our forces are ready to die for Christ, also ready to live for Christ."

Some are only 13. They come from all over Maluku, having made it to Ambon as refugees from outlying areas. All are boys and like any good son, they get their parents' permission to be there. "Those here are ready to leave their parents to defend the faith. If there is armed contact, we are prepared to go straight in. What is important is defending the faith," said their leader.

Faith is a big issue these days for Ambon's beleaguered Christians. After a series of onslaughts by well-armed Muslim forces, at least half the city is in ruins. The Christian side time and again has run out of ammunition but held on, something they believe is due to their faith. When they run out of ammunition, they pray as hard they can, sing hymns and hope God will save them.

So far He has. But their opponents on the Muslim side are also fighting their own holy war, a "jihad", and believe God is on their side too.

God was certainly on the side of 15-year-old Rano Imlobla. During one street battle, a grenade bounced off his head. He emerged unhurt, but the man next to him was killed. Rano is still with the "gnats" and, like all of them, is prepared to die if he has to.

As he drags heavily on a cigarette, commander Tommi shows a couple of samples of bombs conveniently on hand and offers to make some in exchange for money.

On former battlefields, they sometimes find unexploded mortar rounds and grenades. Although still active, they take these weapons apart and find the "yellow medicine" inside, their way of describing the explosive chemicals. The yellow medicine gets stuffed into curved pipes, or wrapped up in packets with nails tied together with sticky tape and wire.

The user injects another liquid into the end with a medical syringe, shakes it about a bit and then lets fly within a second or two. Wait much longer and it would blow up the bomber not the enemy.

Weapons like this have helped change Ambon from a tropical paradise to the picture of devastation it is today. At several stages last year, Christian areas of the city and the rest of the island faced wave after wave of Muslim attackers, often with the support of the Indonesian troops.

Christian leaders have video evidence showing soldiers in full uniform fighting alongside local Muslims in skullcaps.

When that happens, Tommi's boys skip school to go and fight. Their teachers let them. If they did not, the boys would burn down the school, they say.