MADRID (AFP) - A Spanish zoo vet shot a keeper with a tranquillizer dart when a gorilla escape drill went awry, knocking out the unfortunate victim, who spent the next three days in hospital.

Zoo workers ran a drill simulating a gorilla escape on Monday, said the Loro Park zoo, a popular holiday destination in Lanzarote on Spain's Canary Islands off the coast of Africa.

But a park vet armed with a tranquillizer gun then shot a loaded dart into the 35-year-old keeper by mistake, Loro Park spokesman Patricia Delponti told AFP on Friday.

"For an unknown reason it fired accidently and hit his co-worker beside him in the leg," Ms Delponti said.

"The dart was loaded to neutralise a 200kg gorilla. So when it goes into a human weighing about 100kg it is very dangerous," she explained.

The vet reacted by injecting a gorilla tranquillizer antidote into the keeper.

An ambulance then rushed the victim to intensive care at the University Hospital of Tenerife, where he was aroused from his slumber nearly eight hours later, the spokeswoman said. "He was obviously very woozy because of the tranquillizer dose he had received."

After two days in intensive care and a day under observation, doctors discharged the keeper on Thursday morning.

Ms Delponti denied a Spanish newspaper report that the keeper had been dressed in a gorilla suit, confusing the vet who then shot him with the dart.

"He was not disguised as a gorilla and was not wearing a hairy costume, and the vet did not get confused," she said. "It is impossible to confuse a gorilla with a human."