Head of the Syrian Negotiation Commission (SNC) warned on Saturday of the possibility of a genocide being committed against trapped civilians in the besieged rebel-held enclave of Eastern Ghouta that has come in recent weeks under a brutal regime offensive. Nasr al-Hariri slammed the use of chemical weapons against civilians as the greatest crime in Syria, describing the violations that have been committed there as terrible. He accused during a press conference the United Nations of failing to prevent violence raging in the war-wracked country, including the assault on Eastern Ghouta. "We hold the United Nations, the Security Council and the international community ... directly responsible for their silence around these crimes and for failing to take action to prevent these crimes," he told reporters in Riyadh. "But let us not forget that the party that holds direct responsibility for the crimes are the Syrian regime and the countries that continue to stand by it". There can be no political solution in Syria without implementing the agreements reached at the Geneva talks, he added, while urging the international community to exert pressure for the political solution to be adopted. Russian-backed Syrian regime forces have waged a blistering assault on Eastern Ghouta that has retaken 70 percent of the enclave near Damascus since February 18. The offensive has killed around 1,400 civilians, according to the Syrian Observatory for Human Rights, a Britain-based war monitor which relies on a network of sources on the ground. The assault has sparked an exodus with more than 40,000 civilians pouring into surrounding regime-held areas over the past 48 hours. Hariri also addressed the Turkish offensive in Afrin, demanding the Syrian Democratic Forces (SDF) to withdraw from the region, saying that it had “committed violations.” More than 350,000 people have been killed and millions displaced since the Syria war broke out in 2011 with the brutal repression of anti-regime protests.