The zookeeper, who is in a serious condition in hospital, suffered head and chest traumas and open fractures on both arms.
A gorilla at Madrid Zoo has attacked a keeper leaving her with two broken arms and a head injury, the zoo announced on Sunday.
The woman, 46, was performing routine daily tasks at around 10.15 am local time on Sunday morning in an area of the animal's enclosure that is protected by a triple door system when she found herself face to face with Malabo, the zoo's 29-year-old male gorilla.
"The zoo team managed to keep the animal away and later a veterinary team anesthetised it with a tranquillizer dart. The animal was brought to its interior enclosure where it was calmed down," the zoo said in a statement.
"The reasons why the animal was able to access the area are being investigated internally, however, the judicial investigation will determine the exact details," it added.
According to reports, the animal was "startled" just before eating his breakfast and then pounced on the keeper.
"It shook her but without using the enormous strength which it is capable of owing to its 200kg weight," a spokesperson for the zoo said.
The keeper, who has worked at the zoo for 19 years, was intubated and hospitalised in a serious condition, emergency services said.
The woman suffered a head injury, a chest trauma with multiple fractures and open fractures in both her arms.
The zoo said Malabo has been raised by caretakers since birth and is usually "close to caregivers".