Armed zookeepers and police were called to respond after the animal escaped its enclosure - trapping guests inside the park.
Terrified visitors were left hiding out as armed police and animal specialists were deployed to hunt for the roaming animal.
Despite Kumbuka only getting into the secure keepers' area, the Born Free Foundation said it was a "startling reminder" of the risks of keeping wild animals in captivity.
Visitors to ZSL London Zoo described fearing for their safety as they were ordered to take cover in buildings when the mammal got out of its den.
Adding: 'We're happy to report that he's up and grumbling, and interacting with the rest of his family in his gorilla kingdom'.
Scotland Yard said: "Police were called by security at Regent's Park at 5.17pm to reports of an ongoing incident".
Another zoo goer, Dr Jonathan Mall, tweeted: "Gorilla on the loose?"
Host John Humphrys pointed out that although the gorilla only got into the secure keepers' area rather than public areas of the zoo, "it does raise more questions about whether we should be keeping such huge and unsafe animals caged up in the first place".
"It's been subdued, we didn't have to do anything - it was zoo staff", a spokesman told The Telegraph.
Jonny Briers, 22, told the Evening Standard: "We were at the gorilla enclosure and the gorilla charged at the glass". It didn't break it, we saw it do it earlier in the day as well. Others set up parody accounts lambasting the gorilla's escape.
Kumbuka is understood to be one of at least seven gorillas at the zoo's £5m Gorilla Kingdom, which was opened in 2007 by the Duke of Edinburgh.
Officials are yet to comment on how the animal managed to escape its enclosure.
In May, a gorilla was shot dead at the Cincinnati Zoo after it grabbed a 4-year-old boy who had fallen into a moat.
Whether or not the animal was making a statement for Harambe is anyone's guess, but what we do know is that this move speaks volumes on the nature of zoos and whether or not they provide a good atmosphere for animals.
A report via the mirror tells of the gorilla colony being led by male silverback Kumbuka, who parented his first offspring - a baby girl named Alika - with mate Mjukuu in 2014.