The men who attacked Katie Gee and Kirstie Trup with acid in Zanzibar were part of a radical Islamic group that wants to impose stricter Muslim laws on the Indian Ocean island.
Five men have been arrested by police in relation to the attack - two men threw acid in Gee and Trup's faces before speeding off on a moped.
Religious leaders cited by the Telegraph say the men were followers of Uamsho, which wants Zanzibar to become independent of Tanzania and to impose stronger sharia laws.
The men were taken in for questioning late yesterday and early this morning in Stone Town, the old part of Zanzibar city where the attack took place. Three of the men arrested have been released, while two have been detained by police.
One of the men being questioned was the shopkeeper who is reported to have had an argument with the women while they shopped for groceries a few days ago.
Reports suggest the attack had been planned. "The two attackers passed by several white tourists in the area and threw acid after getting closer to [the victims] which raises suspicion of a planned attack," said Bashir Ismail, of Art in Tanzania, the charity Gee and Trup were working for.
Gee was also attacked on a separate occasion two weeks ago. She was hit by a Muslim woman for singing during Ramadan, in an incident that left the 18-year-old "shocked". Another friend suggested the pair were targeted for being Jewish.
Zanzibar police announced a £4,000 reward for information leading to the capture of the men who attacked Gee and Trup.
Both women are currently on board a specially chartered flight back to the UK and are due to arrive imminently.
After landing, it is believed they will be taken directly to a private hospital where they will be treated for their injuries by consultants and surgeons. Both women suffered burns to their faces, chests and hands.
Jeremy Gee said his daughter's injuries were "horrendous" and "beyond imagination", but doctors at the Dar es Salaam hospital in Tanzania said they would not leave scars and could have been much worse.
The doctor said the acid had been diluted, describing the burns as "quite mild". Mkadam Khamis, regional police commissioner in Zanzibar, added: "The doctors said the injuries are relatively minor. There is discoloration but they are not expected to be scarred. They are very lucky in that respect."
It is thought the women ran into the sea following the attack to wash off the acid, which helped to reduce the burns.