An annoyed chimpanzee at Alipore zoo threw stones at visitors on Sunday afternoon, injuring a homemaker and her six-year-old daughter.

Mithu Mondal, 30, and Nikita, who live in Naihati and had come to the zoo with family members, were hit on the head and taken to SSKM Hospital. They were discharged after treatment.

“Some of the visitors threw pieces of bricks at a chimpanzee named Babu. He became furious and retaliated by throwing stones at them,” said S.K Chowdhury, the director of the zoo.

Witnesses said around 12.30pm, some of the people who had gathered around the chimpanzee enclosure started throwing stones and bananas at Babu.

When the primate responded in kind, there was panic. Many ran for cover. Others ducked to avoid the missiles.

The zoo authorities said they would discuss ways to prevent visitors from throwing things at animals. Most enclosures bear the sign “Do not tease or feed wild animals” but a large number of visitors do exactly that.

Last December, Babu and a female chimpanzee had escaped from their enclosure by breaking the lock.