The two women, aged 18, who are charity workers, had the corrosive substance thrown at them as they walked through the island’s capital Stone Town on Wednesday.

The sustained injuries to their faces, chests and hands which are said not to be life threatening.

“We are aware of an incident and are providing consular assistance,” said the Foreign Office.

The women have been named as Katie Gee and Kirstie Trup, according to The Mirror.

The teenagers were working as volunteers on a voluntary trip organised by gap year and volunteering specilist i-to-i Travel

In a statement, the company said: “i-to-i Travel is working with the authorities in their investigations and continue to liaise closely with the British consulate in Tanzania.

“The motive for the incident is as yet not known and we will await the report from the local authorities in Zanzibar before any comment can be made.

“The female clients had been volunteer teachers on Zanzibar and were in the final week of their trip.

“The safety of our customers is of paramount importance to us and our own investigation will be launched as soon as it is possible to do so and more information will be released as it becomes available.”

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