An Egyptian NGO warned today that at least one of the sharks believed to have mauled tourists swimming in Sharm el-Sheikh this week was still at large as the Red Sea resort town reopened its beaches.

Government conservation experts have said they captured two sharks, an oceanic whitetip and a mako, they believed had mauled the Russian and Ukrainian swimmers on Tuesday and Wednesday in the Red Sea.

The resort's mayor, Gamal al-Mahdi, told AFP the beaches were reopened after authorities determined there was no further threat off the coast, which attracts between three and four million tourists a year.

But the Hurghada Environmental Protection and Conservation Association said in a statement that at least one of the sharks caught was not involved in the attacks.

"Comparing the photographs of the oceanic whitetip shark responsible for the second attack with the images of the captured oceanic whitetip shark, it is clear that they don't show the same individual," the group said.

But a government official who oversaw the hunt told AFP the captured oceanic whitetip was the same one filmed by a diver minutes before it surfaced to bite off one of the swimmer's arms and another's foot.

The captured mako, which mauled a third swimmer a day later, was identified by witnesses, according to Mohammed Salem, director of South Sinai Conservation.

Medics had reported a fourth victim of the sharks but Salem said the swimmer cut himself on coral as he fled. Three Russians and a Ukrainian were initially reported to have been mauled, with the victims hospitalised in Cairo.

Salem acknowledged that no limbs were found in the sharks' stomachs.

Sharks have been known to bite off a human limb but not to swallow it. Some experts believe they confuse humans for natural prey and call off the attack when they discover their mistake or become startled by the commotion.