Lai Seng Sin / AP

A siamang like this one photographed in a cage at the National Zoo in Kuala Lumpur, Malaysia, attacked two children Tuesday.

MALACCA, Malaysia — A 3-year-old boy was seriously injured in the right thigh when he was attacked by an 83-pound gibbon at the Malacca Zoo, zoo officials said Thursday.

The boy, identified as Afiq Haziq Kamarul, underwent a three-hour operation at Malacca Hospital after the incident, which occurred Tuesday afternoon, the New Straits Times reports.

Read the full story at New Straits Times

Afiq's mother, Anita Sulaiman, told the paper that the gibbon — specifically, a siamang, a tailless variety with black fur — appeared tame and was allowed to move freely among visitors.

"Suddenly, the group of people who were standing near the gibbon started running away from it and shouted for help," she said.

The gibbon let go only when another visitor kicked its stomach, she said.

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Agence France-Presse reported that the gibbon had earlier bitten a 5-year-old visitor on her right ankle. She also received medical treatment, according to Ahmad Azhar Mohammed, the zoo's director.

Mohammad said zoo officials subsequently caught the gibbon and have quarantined the animal. The zoo is investigating how it jumped out of its enclosure, he said, adding that the animal could have been provoked by the visitors.

A spokesman for the zoo told the Daily News of Malacca that zoo officials had apologized to the family and would help pay Afiq's medical costs.

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