Updated

Four climate change activists scaled gates at Queen Elizabeth II's Buckingham Palace home on Saturday and locked themselves to railings in a protest demanding more urgent action to cut greenhouse gas emissions.

The group, from the Climate Siren environmentalist movement, wore T-shirts with the slogan "Climate emergency. 10 percent annual emission cuts" and chanted through a loud hailer.

London's Metropolitan Police said the four had climbed up a gate at the front of the palace and secured themselves to it, sitting with their legs through the railings.

The protesters unfurled a banner quoting a 2008 speech by Prince Charles, the queen's son and heir, warning over a lack of progress on tacking climate change. It read: "'The doomsday clock of climate change is ticking ever faster towards midnight."

In a letter to the queen posted to the group's website, the activists said they were carrying out their protest in the hope of drawing attention to stalled progress on environmental issues.

"It is time that you and all public figures with influence followed the example of your son by speaking up loudly ... about the escalating threat of catastrophic climate change," the group said.

About 100 people stood at the scene, watching the protest.

Siobhan Grimes, a 24-year-old from east London, said she agreed that there was a need for more urgency on green issues.

"Our politicians aren't doing enough. We're hoping to inspire people to wake up to the consequences of catastrophic climate change," she said.

The queen was not at the palace Saturday, since she was attending a horse racing event in Ascot, southern England.