Kirstie Trup, left, and Katie Gee
Kirstie Trup, left, and Katie Gee, are in a \'stable condition\', receiving treatment at a specialist burns unit in London

A radical Muslim preacher suspected of inciting the acid attack on two British teenagers in Zanzibar has been shot trying to evade capture, police on the East African island said.

Sheikh Issa Ponda Issa was arrested after being hit in the shoulder with a tear-gas canister as he attempted to escape from officers near Dar es Salaam on the Tanzanian mainland.

Sheikh Ponda was being held under police guard in hospital, where he was said to be in a critical condition.

A manhunt was launched after suspicions arose as to his possible role in provoking the attack on gap-year volunteers Kirstie Trup and Katie Gee, both 18.

Gee and Trup were said to be in a stable condition, "well rested, comfortable and relaxed", and continue to receive treatment at the Chelsea and ­Westminster hospital in west London.

Five men are being questioned over the incident, in which the teenagers were attacked by men on a motorbike, according to police on the island.

Two other suspects are still being sought by police, while seven others have been released following questioning.

Sheikh Ponda is thought to have returned to the island a week ago to drum up ­anti-government protests.

He is accused of inciting the attackers into carrying out the ambush in the hope of raising the profile of his ­campaign to rid Zanzibar of ­foreigners and impose sharia law.

Sheikh Ponda was previously arrested in October 2012 for stoking religious hatred after Muslim protesters burned five churches. He was released in May.

He has been linked to the radical Islamic group Uamsho, which is ­suspected of involvement in an acid attack on a moderate imam, and the murder of a Catholic priest.

The women were celebrating the end of their trip as volunteer teachers on the island when a corrosive substance was thrown at them in an apparently random attack.

The girls, who had been working in ­Zanzibar City, ­suffered ­appalling burns and trauma.

It has since emerged that they may have been targeted for being Jewish. The island's population is overwhelmingly Muslim.

Zanzibar's assistant police commissioner Mkadam Khamis Mkadam said: "They were accosted by two men riding a motorcycle. They poured this liquid - we suspect it was acid - before they ran away."

The women had planned to return to the UK in time to collect their A-level results next week.

Trup had been hoping to study history at the University of Bristol while Gee was considering the University of Leeds.

Families of both teenagers have been at their bedsides at the hospital's specialist burns unit since the ­teenagers were flown home on Friday.

Katie has tweeted: "Thank you for all your support x".

The Foreign Office meanwhile came under pressure to upgrade its travel warning, including from Tory MP Bill Cash, who sits on the all-party parliamentary group for Tanzania.

He said the crime was "more than just an ordinary criminal event", and added: "People need to be extra vigilant and the Foreign Office and High Commission need to make a very thorough evaluation of the threat, as these latest attacks would seem to be on religious grounds.

"The threat to tourists going to Tanzania and Zanzibar needs to be upgraded without doubt."

The Foreign Office previously updated its Tanzania travel advice page on Friday, warning British nationals to "take care" in light of the attack.