A man who scaled the lower sections of Big Ben's Elizabeth Tower at London's Palace of Westminster has been arrested after coming down from his perch after 16 hours.

Traffic around the Palace of Westminster in London came to a standstill for much of Saturday as emergency crews tried to reach the man who climbed the Big Ben tower holding a Palestinian flag.

He was waving the flag and shouting "free Palestine", according to British media.

"We worked with other agencies including the London Fire Brigade and deployed specialist officers to bring this incident to a close as quickly as possible whilst minimising risk to life," a police spokesperson said.

Negotiators were lifted up on a fire brigade ladder platform several times before eventually talking him down.

Man who scaled Big Ben's clock tower with Palestinian flag comes down. – AP

The barefoot man, who appeared to be staging a protest on a ledge several metres up Elizabeth Tower, which houses Big Ben, stepped off the building and onto a cherry picker after a long conversation with negotiators. He got into a waiting ambulance.

Emergency services closed Westminster Bridge on Saturday morning in response to the incident, and parliamentary tours were also cancelled. Police also blocked off all pedestrian access to Parliament Square.

The Metropolitan Police said earlier that officers received reports about the man around 7am Saturday and were “working to bring the incident to a safe conclusion" alongside firefighters and ambulance services.

A small group of supporters shouted “Free Palestine” from behind a police cordon nearby.

Emergency services attend after man with a Palestine flag climbed up Elizabeth Tower, which houses Big Ben. – AP