The World Health Organization announced on Wednesday that around 500 people from Syria’s Douma town displayed symptoms of exposure to toxic chemicals. "In particular, there were signs of severe irritation of mucous membranes, respiratory failure and disruption to central nervous systems of those exposed," the United Nations health agency said in a statement issued in Geneva. WHO also said that more than 70 people sheltering from bombardment in basements in the former rebel pocket of Eastern Ghouta, where Douma is located, have died. It said 43 of those deaths were "related to symptoms consistent with exposure to highly toxic chemicals," citing reports from its local health partners. "We should all be outraged at these horrific reports and images from Douma" where Saturdays attack took place, said Peter Salama, the UN agencys chief of emergency response. "WHO demands immediate unhindered access to the area to provide care to those affected, to assess the health impacts, and to deliver a comprehensive public health response," he said. UN aid agencies lack access to most of Eastern Ghouta, from which rebels are withdrawing under a deal with the Syrian regime that restored its control over the region. WHO said it had trained more than 800 Syrian health workers to recognize symptoms and treat patients for chemical weapons exposure. The UN agency has also distributed antidotes for nerve agents, including in besieged Douma last year. UN officials have also accused regime forces of at times removing those treatments from humanitarian vehicles. Tens of thousands of civilians remain trapped in Douma, the UN refugee agency UNHCR said on Tuesday, and it demanded access to the area. More than 133,000 people are estimated to have fled a desperate humanitarian situation in Eastern Ghouta over the past four weeks, UNHCR added. The United States, Britain and France have argued that Saturday’s attack bears all the hallmarks of a strike ordered by the regime of Bashar Assad. Assad has been blamed for previous attacks by the Organization for the Prohibition of Chemical Weapons (OPCW) and UN-backed war crimes investigators. US President Donald Trump and Western allies are considering military action to punish Assad for the Douma assault. Damascus said reports of a gas attack are false. Russia and the United States clashed at the United Nations Security Council on Tuesday after Moscow vetoed a Washington-drafted resolution to set up a panel to identify the perpetrators of the Douma attack. It was the 12th time that Russia has used its veto power at the council to block action targeting its Syrian ally. The council voted two more times on draft texts put forward by Russia, but both measures failed to garner the nine votes required for adoption, laying bare divisions at the top UN body over Syria. US Ambassador to the UN Nikki Haley said Russia was to blame for the councils failure to take action on Syria, now in its eighth year of war. "Russia has trashed the credibility of the council," she said. "History will record that, on this day, Russia chose protecting a monster over the lives of the Syrian people."