France Has 'Proof' Chemical Weapons Used France says tests on chemical samples taken from Syria prove the deadly nerve agent sarin gas has been used several times during the civil conflict. Foreign minister Laurent Fabius made the announcement on Tuesday, citing tests carried out by a French laboratory, but did not give any details of where or by whom the poison gas had been used. He said: "These tests show the presence of sarin in various samples in our possession. France is certain that sarin gas was used several times in Syria in limited areas. It would be unacceptable that those guilty of these crimes remain unpunished. He added that the test results had been handed to the United Nations. British Foreign Secretary William Hague said he welcomed the decision by France to share the information related to the samples with a UN investigation. "The scale of the atrocities being committed by the Assad regime is becoming ever clearer," he said. This announcement adds further weight to the need for a full and unimpeded investigation into all relevant incidents. The UN investigation team must be allowed unrestricted access to investigate on the ground in Syria and we call on the Assad regime to fully cooperate with it. The US said more work needed to be done to establish who was responsible for the use of sarin gas, the amount used and the circumstances in which the chemical weapon was used. Laurent Fabius, France's foreign minister White House spokesman Jay Carney said: "As the President (Barack Obama) made clear, we need to expand the evidence we have, we need to make it reviewable, we need to have it corroborated before we make any decisions based on the clear violation the use of chemical weapons would represent." Sky's US Correspondent Amanda Walker said both sides have been accused of war crimes. She said the UN had been allowed to investigate a claim by the government that opposition forces had used chemical weapons in an attack on March 19 near the city of Aleppo, but not any other. "They do have a Swedish-led team that they want to put into Syria," she said. They have been denied entry to investigate further claims that the government has been using chemical weapons, the opposition say, in at least six attacks. She added: "Sarin is one of the most deadly chemical agents in the world - a single drop can kill a person, inhaled or absorbed." UN investigators had earlier said there were "reasonable grounds" to believe chemical weapons had been used in Syria. The organisation's human rights group said it had received allegations that both the country's government and rebels had used limited quantities of toxic substances, but most testimony related to their use by state forces. Paul Pinheiro, the chair of the commission, said: "It has not been possible, on the evidence available, to determine the precise chemical agents used, their delivery systems or the perpetrator." The inquiry examined four reported toxic attacks in March and April, interviewing victims, medical staff and refugees who had fled the affected areas. But the team behind the investigation said the inconclusive findings show that full access to Syria is needed for the UN to form a complete picture of the atrocities. Syrian army soldier sits in his tank in Qusayr The 29-page report on human rights abuses in the ongoing civil war also described war crimes and crimes against humanity which have reached "new levels of brutality." Leaders of Syria's military and government were accused of "a concerted policy" of violations, including the bombing of cities and executing of civilians, which investigators said they must be held accountable for. The conflict has now lasted for 26 months and claimed more than 80,000 lives. The UN report blamed both government and rebel forces for carrying out murder, torture and rape, but said the intensity and scale of the crimes committed by the state outweighed those committed by opposition fighters. Details of various recent massacres were also given, with evidence pointing to government-backed militia for the killing of dozens of women and children in the villages of Baida and Banias in May. In a separate case linked to rebels near Deir al Zor, investigators said they believed that a child took part in the beheading of two kidnapped soldiers. The total number of massacres committed in Syria since September now stands at 30. Earlier Russian President Vladimir Putin defended his country's right to sell arms to the Syrian government but added that they had not yet delivered S-300 missile systems. Speaking after a summit with EU leaders in Yekaterinburg, Putin also emphasised his belief that any foreign military intervention in the civil war was doomed to fail.