Four people have been arrested after climate action protestors blocked the entrance of a huge coal mine. Extinction Rebellion protestors have been occupying an area outside the main gates of Ffos y Fran in Merthyr Tydfil, the largest opencast coal mine in the UK, on Thursday.

The climate group posted on social media on Thursday saying a number of police vehicles had arrived at the mine, which was ordered to close after 15 years when Merthyr Tydfil County Borough Council voted in April to refuse extending operations there.

The mine has been hugely controversial in recent years with residents complaining over noise, pollution and disruption to their lives. Since then, campaigners claim mining has continued unlawfully at the mine. Merthyr (South Wales) Ltd, which operates the site, recently made a last-ditch appeal against the decision to stop operations there.

Read more: Living in the noise, dust and pollution of the UK's largest open coal mine at Ffos-y-Fran

Extinction Rebellion wrote on Twitter on Thursday that police had arrived at the mine where some protestors had chained themselves to a large pink boat in front of the mine's entrance. It is believed they have been at the site since Wednesday. It is the first action by members of Extinction Rebellion using ‘lock ons’ since the Public Order Act (2023) came into effect in May. Under the Act, locking-on is now an offence which can result in 51 weeks in prison.

The group claims the mine is continuing to operate despite planning permission running out in September. Recently barristers for climate action claimed that continued coal extraction at Ffos y Fran was illegal. The company behind the mine, Merthyr (South Wales) Ltd, confirmed on Wednesday that an appeal has been lodged with Welsh ministers, adding: "It would not be appropriate to comment further whilst the appeal process is ongoing."

South Wales Police has confirmed four people were arrested on suspicion of aggravated trespass on Thursday. Three women, a 43-year-old from Exeter, a 45-year-old from Dorset and a 75-year-old from Llanidloes, as well as a 68-year-old man from Caerphilly, have been taken to Merthyr Tydfil police station.

Superintendent Michelle Conquer said: “Since Wednesday afternoon, police officers have been deployed to the Ffos y Fran site in Merthyr Tydfil to facilitate peaceful protest.

“In doing so we note the views of the protest group that the mine is operating unlawfully. We have engaged with the mine operator and other stakeholders across our communities in order to balance the respective rights of the parties involved.

“The protest group has engaged in acts of trespass and have deployed lock on tactics at the location. A number of protestors chained themselves to the entrance gate. Officers have spent considerable time negotiating with the protestors to offer them the opportunity to voluntarily relocate and remove their own lock on equipment. This option was declined or ignored. As a result, four people were arrested on suspicion of aggravated trespass.”

Meanwhile, calls have also been made for Welsh Government to intervene to tell operators of Ffos y Fran to stop mining coal there. Friends of the Earth Cymru have written to Julie James, the climate change minister, asking Welsh Government to use its powers to stop what it says is unlawful coaling.

It wrote to both Welsh Government and Merthyr Tydfil Council requesting a stop notice be issued without delay. Friends of the Earth Cymru said the council have not issued a stop notice to date and are now urging Welsh Ministers to do so as soon as possible.

They said an enforcement notice against the operator of Ffos-y-Fran was due to take effect on Tuesday, June 27 which would have given them 28 days to stop mining, but at the last minute the operator appealed the enforcement order. In their letter, Friends of the Earth Cymru said: “It is imperative [Welsh Ministers] take this action immediately to stop any further extraction and to limit any further, irrevocable, harm to the climate. As you will know we are in a worsening climate emergency. The continued coaling will only add to this, to the detriment of current and future generations.”

Friends of the Earth Cymru said that Coal Action Network have calculated that over 1000 tonnes of coal is being taken from the ground every day, which is “the CO2 equivalent of burning 1.5 million litres of petrol.” Friends of the Earth Cymru said that the appeal process could take many months – during which it is feared that mining will continue at the site if action is not taken.

Merthyr Tydfil Council has been contacted for comment. To get more Merthyr stories straight to your inbox, subscribe to our daily newsletter here.