Two foreign nationals were arrested after they allegedly trespassed into the enclosure of a Japanese macaque who went viral for clutching an orangutan plushie after being rejected by his mother at a zoo near Tokyo.

They were arrested on Sunday after one of them, dressed in a yellow costume, scaled the fence inhabiting the monkey at the Ichikawa City Zoo in Chiba prefecture, while the other filmed him with a smartphone.

The two are alleged to be US nationals, reported Kyodo News.

Police identified the two men as 24-year-old Reid Junai Dyson and 27-year-old Neil Jabari Duane, according to News on Japan.

At around 11am on 17 May, Mr Dyson allegedly climbed over the fence and jumped four metres into the enclosure, reported the outlet.

About 60 monkeys, including Punch, were inside the enclosure at the time. Mr Dyson was held by the zoo staff and handed over to the police.

The Independent has reached out to the US embassy in Japan seeking a response.

Punch, the baby orphan macaque, went viral earlier this year, after he was seen hugging an orangutan stuffed toy given to him as a substitute for his mother when other monkeys shooed the baby away.

Punch was abandoned by his mother after his birth, presumably because of exhaustion. Zookeepers nursed him and gave him the toy to train him to cling, an ability newborn macaques need to survive.

In the months since the incident, the macaque is believed to have been outgrowing the orangutan plushie and socialising, getting groomed and hugged by other adult monkeys.

“Helping Punch learn the rules of monkey society and being accepted as a member is our most important task,” said Kosuke Kano, a 24-year-old zookeeper.

Punch was so popular after images of him and his toy showed up, the zoo had to set rules to make visitors be quiet and to limit viewing to 10 minutes to reduce stress for the more than 50 other monkeys.