The duo, who identified themselves as Vadim Makhorov and Vitaliy Raskalov, said they scaled the Shanghai Tower, which will reach over 630 metres when it is finished this year if construction goes according to schedule. Globally it will be second only to the Burj Khalifa in Dubai, which stands at 828 metres.
The video showed the two, wearing black hoodies, walking up stairs, climbing ladders and finally scaling a crane at the top of the Shanghai Tower as they peered at buildings shrouded in clouds below.
Raskalov said on his blog that they started the ascent on January 31, the first day of China's Lunar New Year.
"At that time the security was less watchful, workers were on vacations," he said.
Also Read
The duo, who use the name "OnTheRoofs", could not be immediately reached for comment. Media reports say they previously climbed the Great Pyramid of Giza.
"My knees are getting weak just by watching. Hollywood blockbusters are nothing compared to this," said one poster.
The building's management said steps would be taken to bar any repeat performances, according to a statement carried by state media.
"Shanghai Tower will implement measures such as putting up wire fencing around the walls and installing safety doors on exits to avoid similar incidents from happening again," said the statement, which was carried by state television.