The Foreign Secretary, William Hague, said the government believes a chemical attack in Syria has been carried out by forces loyal to President Assad. The global response to the allegations has been gathering pace with President Obama calling it "a big event of grave concern". The Syrian government is still refusing to allow UN inspectors into the area.
Mr Hague said they must be allowed to establish the truth:
"It's now 48 hours since the reports started to come in of what seems to have been a terrible atrocity near Damascus including the use of chemical weapons.
"People will have seen some of the film footage of the people, including so many children, affected and, clearly, many hundreds of people killed.
"This is not something that a humane or civilised world can ignore. Our priority is to make sure the world knows the facts of what has happened and that means the UN team that is in Damascus, only 20 minutes travel away, being able to get there and to investigate.
"So this is our priority at the moment: to make sure that a UN team can investigate on the ground and establish the facts.
"If that doesn't happen though, within some days, since time is of the essence in these things - the evidence will deteriorate over a matter of days - then we will need to be ready to go back to the Security Council to get a stronger mandate and for the world to speak together more forcefully about this so that there can be access.
"The only possible explanation of what we've been able to see is that it was a chemical attack.
"Clearly many, many hundreds of people have been killed, some of the estimates are over a thousand, there is no other plausible explanation."
The United Nations estimates one million children have fled the conflict in Syria and children make up more than half of all refugees from more than two years of violence. The U.N. described the figure as "a shameful milestone", urging the entire international community to do more to help end the conflict and protect the well-being of "a generation of innocents." Most have found a haven in neighbouring countries Lebanon, Jordan, Turkey, Iraq and Egypt. Increasingly, they are also fleeing to North Africa and Europe.
Executive Director of the UN Children's Fund (UNICEF) Anthony Lake said:
"This one millionth child refugee is not just another number.
"This is a real child ripped from home, maybe even from a family, facing horrors we can only begin to comprehend.
"We should stop and ask ourselves how, in all conscience, we can continue to fail the children of Syria."
Alan Thomlinson is the Emergency Programme Manager for Syria for the Catholic aid charity CAFOD. He told Premier's Marcus Jones on the News Hour of the difficulties they are facing:
The U.N. said the majority of child refugees, some 740,000, are under the age of 11, and more than 3,500 children in Jordan, Lebanon and Iraq have crossed Syria's borders either unaccompanied or separated from their families, making them vulnerable to multiple threats including child labour, early marriage and the potential for sexual exploitation and trafficking. Inside Syria, some 7,000 children have been killed during the conflict, and UNHCR and UNICEF estimate that over two million have been internally displaced.
High Commissioner for Refugees António Guterres said:
"What is at stake is nothing less than the survival and well-being of a generation of innocents.
"The youth of Syria are losing their homes, their family members and their futures. Even after they have crossed a border to safety, they are traumatized, depressed and in need of a reason for hope.
"We can really talk of the enormous risk of Syria facing a problem of a lost generation."
China has said no side should rush to pre-judge the results of any U.N. investigation over the alleged use of chemical weapons in Syria. Rebels in the country accuse the Assad regime of ordering a gas attack that killed more than 1,000 people on Wednesday. U.N. Secretary-General Ban Ki-moon said he's "troubled" by allegations that chemical weapons were used in an attack near Damascus.
Speaking in the South Korean capital, Seoul, he said there must be an investigation and has given this warning:
"Any use of chemical weapons, anywhere by anybody under any circumstances, would violate international law.
"Such a crime against humanity should result in serious consequences for the perpetrator."
The Syrian government denies using chemical weapons, saying the reports are "absolutely baseless". Russia says the Syrian government should co-operate with any United Nations inquiries. The United States said that if reports of a chemical weapons attack in Syria are true, it would be an "outrageous and flagrant escalation" by the Assad government. President Obama has asked US intelligence agencies to investigate the alleged use of poisonous gas near Damascus. Last year, President Obama said the use of chemical weapons in Syria would cross a "red line" and force a tough US response. In an interview broadcast on CNN on Friday, he said the recent claims of chemical weapons use were "very troublesome".
Meanwhile, an Italian Jesuit priest who disappeared last month in eastern Syria is still unaccounted for.
Father Paolo Dall'Oglio, who supports the uprising against President Assad, disappeared in the rebel-held city of Raqqa on July 29th, 2013.