A police officer can be seen in the live video feed from a camera worn by one of the climbers at the top of The Shard. It is not clear whether any of the protesters have been arrested.
Greenpeace reports that its six protest climbers have reached the top of The Shard in London, although live TV footage shows only one of them at the pinnacle.
The six women who are scaling The Shard building in London are just 18 metres from the top, according to Greenpeace press officer Ben Stewart.
One climber has been nominated to "free climb" the final ascent, meaning she will use no aids such as ropes.
The #iceclimb women are 18m from the top. they've chosen Wiola, 23, from Poland to make an attempt on the summit. She's going for it. Now.
One of the Shard climbers, Liesbeth Deddens, has tweeted that she is not ready to give up on reaching the top after 16 hours of climbing:
#iceclimb It is getting late.been going 16hrs and im tired.but not ready to give up with top in side.bit support?
Ali Garrigan, currently one of six Greenpeace activists climbing exterior of The Shard, is still in "great spirits", Greenpeace said today after speaking to her.
The London Ambulance Service has tweeted that members of its hazardous area response team remain on standby at The Shard. They were reportedly called to the protest at 4.40am this morning.
Greenpeace has tweeted brief biographies of five of the six women who are climbing The Shard as a protest against fossil fuel companies drilling in the Arctic.
Sabine (top left) was "inspired to train as a climber after helping other activists get ready in Belgium".
Sandra (top centre) is from Sweden and has "just finished an MA in environmental science". She is also the lead climber.
Wiola (top right) from Poland "wants to change the way companies exploit vulnerable regions like the Arctic".
Liesbeth (bottom left) is from the Netherlands and "began climbing in high school". She now climbs ice, rock, alpine as well as The Shard.
Ali (botton right) is the only British protester. She has been climbing since she was 18 and hopes the protest can "bring attention to the dangers facing the Arctic".
The sixth climber is Canadian Victoria and is taking part because she "wanted to shout about something from the rooftops".
Environmental charity Greenpeace has tweeted this photo of the Shard climbers taking part in a training exercise yesterday. They appear to be using a ladder to climb through a hatch in the roof of a lorry.
The training appears to have been aimed at the first stage of the climb when the protesters emerge from a lorry via a ladder to start the ascent.
The Deputy Prime Minister has said he disagrees with activists climbing The Shard today, deeming it to be "dangerous".
Asked about the Shard protest during his call-in show on LBC 97.3 radio Nick Clegg said:
"Of course what they are doing looks extraordinary on the telly, (but) I don't actually support them doing something like that, which is going to tie up a lot of police time and is obviously quite dangerous.
"I really do think that they could get their point across to the companies which they are seeking to address in a different way."