A man who climbed Big Ben's Elizabeth Tower at London's Palace of Westminster waving a Palestinian flag early on Saturday has come down after 16 hours, according to Sky News.

Local media reported he shouted "free Palestine".

Emergency crews had gone up in a crane to negotiate with the man, and he came down after earlier telling negotiators he would come down "on his own terms", according to the Sky News report.

A spokesperson for the Metropolitan Police earlier said they were alerted to the incident at Elizabeth Tower (Big Ben) at 0724 GMT.

"Officers are at the scene working to bring the incident to a safe conclusion. They are being assisted by the London Fire Brigade and the London Ambulance Service," the spokesperson said.

Emergency services closed Westminster Bridge on Saturday morning in response to the incident, and parliamentary tours were also cancelled, according to Sky News. (Reuters)