Two US nationals have been arrested after one jumped into the enclosure of an internet-famous monkey at a Japanese zoo while the other filmed the stunt, police have said.

One of the men, who claimed to be a 24-year-old college student, is accused of scaling a fence to gain access to Punch's enclosure on Sunday morning. The other man claimed to be a 27-year-old singer.

Both have denied the allegations. Police have said no monkeys were injured during the incident.

Clips of the now nine-month-old macaque attracted millions of views online earlier this year after it was spotted hugging an stuffed toy orangutan given to him by keepers at Ichikawa City Zoo after he was rejected by his mother.

Footage purportedly of Sunday's incident filmed by other zoogoers and shared on social media shows a person wearing a costume and carrying a stuffed toy jumping over a fence and into the monkey enclosure. The costume was said to be promoting a cryptocurrency.

The person can then be seen being led out by a zookeeper.

The two men held by police over the incident have been arrested on suspicion of forcible obstruction of business, according to local media.

Ichikawa City Zoo said in a statement on Monday that it had filed a damage report with the police and was putting countermeasures in place to prevent future incidents.

These included expanding the enclosure's viewing restriction area and installing intrusion prevention nets, it said.

The zoo added that it was considering a full ban on filming around the monkey enclosure and was putting requests to film from YouTubers temporarily on hold.

The men did not get close to the animals and were quickly apprehended by zoo workers, an Ichikawa Police official said, according to news agency AFP.

Since he moved into the shared enclosure in January, the zoo has regularly shared social media updates on Punch, who first gained attention for his attachment to his soft toy, being seen dragging it around and playing with it.

The zoo previously said Punch initially struggled to bond with the other monkeys, with only the toy and zookeepers providing him company after he was abandoned by his mother.

But recent updates indicate he is integrating with the other macaques - including being hugged by other monkeys and grooming them.

There have been other incidents of people trespassing into zoo enclosures of zoo animals after they became internet sensations.

Last month, a man was fined $300 (£223) for breaking into the enclosure of Moo Deng, an endangered baby pygmy hippo who gained global attention after images of her went viral online, at a zoo in Thailand.