Macedonian police have fired tear gas at more than 500 people attempting to break through a border fence at the Idomeni camp in Greece.

A number of photos and videos on social media appear to show refugees running from gas canisters and stun grenades thrown by officers in riot gear. Others showed people being carried away unconscious. Médecins sans Frontières said it treated more than 300 patients, including 200 for exposure to tear gas and 30 for rubber bullet wounds.

Witnesses said there were a number of loud explosions, as helicopters flew overhead and rubber bullets were fired. They said the fence had been breached at two points.

Laura Samira Naude, an officer at refugee charity Lighthouse Relief, said she witnessed “horrific scenes”.

Ms Naude told The Independent: “The police were firing so much tear gas and rubber bullets too. Young babies had to be treated.

“Some of the refugees were told that the border would be opening up at 9am today. Hundreds of families had their bags packed, ready to leave. They said they don’t want to stay here because otherwise they’ll die.

Horrific scene here in #Idomeni as people are being relentlessly tear gassed #refugees pic.twitter.com/LCwnbfC8O0 — Lighthouse Relief (@LighthouseRR) April 10, 2016

“The asylum system is frankly quite ridiculous. People have to lodge their applications through Skype, but in the camp it’s just not plausible. So their asylum requests aren’t even being processed.”

Jonas Hagensen of Medecins Sans Frontieres told The Independent they were treating people for respiratory problems, open wounds and suspected fracture. The charity revealed they were treating pregnant women.

Mr Hagensen said staff were "badly affected" by the tear gas, and that one patient claimed to have been taken to a room by Macedonian police and beaten for an hour.

Wolly Ahmed, a volunteer at the Idomeni camp, said initially the refugees “waited peacefully on a nearby set of train tracks”.

Mr Ahmed said a group of five refugee leaders went to hold discussions with Macedonian police, but they returned unsuccessful.

He added: “They began surging towards the fence and managed to cut through in two different parts."

Fotis Filippou, director of campaigns at Amnesty International, called on the Macedonian police to "fully comply" with international policing standards.

Mr Filippou added: "The scenes we are seeing are the expected and unavoidable result of thousands being trapped in Idomeni and elsewhere in Greece - abandoned by Europe - in awful conditions and with little hope of getting protection.

"Greece and the EU must work on real solutions as a matter of urgency: these must include adequate reception conditions in Greece and access to relocation and other schemes that will allow refugees to find sanctuary in other EU member states."

Refugees break through Macedonia border fence in February Show all 15 1 /15 Refugees break through Macedonia border fence in February Refugees break through Macedonia border fence in February Stranded refugees try to bring down part of the border fence during a protest at the Greek-Macedonian border, near the Greek village of Idomeni Reuters Refugees break through Macedonia border fence in February Stranded refugees try to break a Greek police cordon in order to approach the border fence at the Greek-Macedonian border, near the Greek village of Idomeni Reuters Refugees break through Macedonia border fence in February Stranded refugees flee tear gas fire by the Macedonian police, after trying to bring down part of the border fence during a protest at the Greek-Macedonian border, near the Greek village of Idomeni Reuters Refugees break through Macedonia border fence in February Stranded refugees try to break a Greek police cordon in order to approach the border fence at the Greek-Macedonian border, near the Greek village of Idomeni Reuters Refugees break through Macedonia border fence in February Stranded refugees in the northern Greek village of Idomeni approach the Greek-Macedonian border as they try to enter Macedonia AP Refugees break through Macedonia border fence in February Macedonian riot police officers stand next to part of the border fence brought down by protesting stranded refugees and migrants during a protest at the Greek-Macedonian border, near the Greek village of Idomeni Reuters Refugees break through Macedonia border fence in February Stranded refugees try to bring down part of the border fence during a protest at the Greek-Macedonian border, near the Greek village of Idomeni Reuters Refugees break through Macedonia border fence in February Stranded refugees break an iron fence and throw stones from the Greek side of the border as Macedonian policemen push them back, near the southern Macedonian town of Gevgelija AP Refugees break through Macedonia border fence in February A girl cries as she flees clashes during a protest at the Greek-Macedonian border, near the Greek village of Idomeni Reuters Refugees break through Macedonia border fence in February Refugees try to broke an iron fence from the Greek side of the border as Macedonian police stand guard, near the northern Greek village of Idomeni AP Refugees break through Macedonia border fence in February Stranded refugees and migrants in the northern Greek village of Idomeni approach the Greek-Macedonian border as they try to enter Macedonia AP Refugees break through Macedonia border fence in February A man helps children to run away after Macedonian police fired tear gas at a group of refugees who tried to push their way into Macedonia AP Refugees break through Macedonia border fence in February A woman carries a child on the Greek side of the border as they run away after Macedonian police fired tear gas at a group of refugees who tried to push their way into Macedonia AP Refugees break through Macedonia border fence in February Refugees run away after Macedonian police fired tear gas AP Refugees break through Macedonia border fence in February A woman falls as refugees with their children run away after Macedonian police Getty Images

The 28 European Union member states last month voted to shut down the so-called “Balkan route”, leaving 42,000 refugees stranded on Greek soil. The Greek interior minister Panagiotis Kouroublis said the conditions at Idomeni, where more than 11,000 refugees currently live, are comparable to Nazi concentration camps.