Zanzibar has offered a reward for information leading to the arrest of men suspected of hurling acid in the faces of two young British women.
Information and Tourism Minister Said Ali Mbarouk said Wednesday's attack on the two 18-year-olds - the first such assault on foreigners in the popular tourist destination - was "a shame on the people of Zanzibar".
He said anyone providing information leading to the arrest of the assailants would be given 10 million Tanzanian shillings ($A5000).
Two men on a moped threw acid at Katie Gee and Kirstie Trup on Wednesday evening as they strolled through Stone Town, the historical centre of the capital of the semi-autonomous Tanzanian archipelago, splashing their faces and chests.
"We have to work harder to make sure that Zanzibar is safe for visitors and citizens," the minister said on Friday.
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Wednesday's incident was the first assault on foreigners in the Indian Ocean island but acid has been used in a number of recent attacks.
The women were flown to Tanzania's economic capital Dar es Salaam for treatment, and then flown home.
The two women were spending three weeks doing volunteer teaching in a local school, a placement organised through i-to-i Travel, a Kent, Britain-based company that organises Gap year volunteer work.
The attack occurred at the end of the Muslim holy month of Ramadan, and as people began to celebrate the Eid al-Fitr holiday.
Tourism is the main foreign currency earner for Zanzibar, famed for its white-sand beaches and historical buildings in Stone Town, listed as a world heritage site by UNESCO.
In Zanzibar, some more conservative elements of the Muslim community object to foreign tourists who wear revealing clothes, as well as bars selling alcohol.
Tanzanian President Jakaya Kikwete, who visited the two young women in hospital in Dar es Salaam, called the attack "shameful" and said it "tarnished the image" of Tanzania.
He ordered the security forces to step up their investigation and find the culprits.
Zanzibar police chief Mussa Ali Mussa said seven people have already been questioned over the attack.
Politicians and religious leaders in Zanzibar also condemned the incident.
