Protesters have locked themselves to the gates of a drilling rig site in a demonstration against fracking.

Up to 20 people are believed to be involved in the protest at Cuadrilla Resources' drilling rig in Danesmoor, Chesterfield.

Four of the demonstrators, who are from anti-fracking group Frack Off, locked themselves to the site's gate in a bid to prevent the rig moving to its fracking site in Lancashire. Fracking is the controversial extraction of gas from shale rock.

Derbyshire Police said they were monitoring the group and that it was a peaceful protest.

Demonstrator Elsie Walker, 27, said: "The scale of development proposed is being completely ignored. Cuadrilla wants to drill 800 wells in Lancashire alone. They are one company going after one type of gas.

"There are several companies going after several types of unconventional gas in the UK and all potentially on a similar scale to Cuadrilla. If this goes ahead, we will witness the total industrialisation of the British countryside and the destruction of the land and water on which we depend. We cannot allow this to happen."

In a statement, Derbyshire Police said: "Police officers are monitoring a group of protesters who are demonstrating outside a drilling company on Old Pit Lane in Danesmoor, near Chesterfield.

"Officers were called at 5.20 this morning by staff at the firm. This is a peaceful protest which is not blocking access to other premises. Officers are talking to the protesters and will remain at the scene until the protest is over."

In a statement, Cuadrilla's drilling contractor, PR Marriott Drilling Ltd, which owns the site, said: "On Monday June 18th at 5am, 20 environmental protesters from a Brighton-based group illegally blocked access to the Chesterfield site of Cuadrilla's drilling contractor, PR Marriott. PR Marriott employs approximately 180 people in the UK, with around 50 people working at the Chesterfield site - most of whom work locally. Despite the best attempts of the environmental protesters to damage this British business, access to the site has been gained and work has all but returned to normal while we wait for the protesters to leave."

Mark Miller, chief executive of Cuadrilla Resources, said: "We would rather concentrate on continuing to communicate on every aspect of our operations with the local communities that we work within than get involved in arguments with environmental protesters - most of whom don't live anywhere near where we work."