Syria, rebels deny using chemical weapons as NGO says 355 people died of 'neurotoxic symptoms'
Syrian state media says regime troops have found nerve gas materials in tunnels used by rebels, after the suspected chemical attack in the capital Damascus last week.
The claim contradicts opposition groups who say the government launched nerve gas at its own people killing hundreds of people - an accusation that has been fiercely denied.
These claims have emerged as United Nations envoy Angela Kane arrived in Damascus to push for a team of inspectors to have access to the site.
The accusations were traded as Prime Minister Kevin Rudd received a national security briefing on the situation in Syria and how Australia should respond.
US president Barack Obama, under mounting pressure to take action if the chemical weapons claims are proven, has also been meeting with his national security advisers to discuss reports of the attack.
The Syrian government has strongly denied the allegations but has yet to accede to demands that UN inspectors already in the country be allowed to visit the sites of the alleged attacks.
However, Syrian information minister Omran al-Zohbi says the regime has never used chemical weapons.
"We have never used chemical weapons in Syria, in any form whatsoever, be it liquid or gas," he told a Beirut-based Arabic television channel.
However, Syrian foreign minister Walid Muallem was quoted by his Iranian counterpart, Mohammad Javad Zarif, as saying Damascus would facilitate a visit of UN inspectors to the scene of the alleged attack.
"The Syrian government will cooperate with the United Nations mission now in Syria to create the conditions for a visit to zones where terrorist groups have carried out attacks with chemical weapons," he was quoted as saying.
"We are currently in the process of discussions with the United Nations mission on preparing this visit."
On Friday, the National Coalition pledged to guarantee the safety of the inspectors but warned that the "clock is ticking" before alleged evidence vanishes.
Meanwhile, Doctors Without Borders (MSF) says around 3,600 patients displaying "neurotoxic symptoms" had flooded into three Syrian hospitals on the day of the alleged attacks and 355 of them died.
The victims all arrived within less than three hours of each other, and MSF director of operations Bart Janssens said the pattern of events and the reported symptoms "strongly indicate mass exposure to a neurotoxic agent".
"Medical staff working in these facilities provided detailed information to MSF doctors regarding large numbers of patients arriving with symptoms including convulsions, excess saliva, pinpoint pupils, blurred vision and respiratory distress," he said.
But MSF stressed it had no scientific proof of the cause of the symptoms nor could it confirm who carried out the attack.
For its part, the Syrian Observatory for Human Rights said more than 300 people had died from the effects of gas, including 82 women and 54 children.
Kevin Rudd attends national security briefing
Last night Mr Rudd interrupted his election campaign attended a national security briefing on the situation in Canberra.
He had been scheduled to spend Saturday night in Brisbane, but diverted his campaign for the briefing with officials, including Foreign Minister Bob Carr and Minister for Defence Materiel, Mike Kelly.
Asked earlier in the day about whether Australia would participate in a US or UN-sanctioned military intervention, Mr Rudd said the first step was to establish the facts of the attack.
"We have, together with the US, grave concerns as to what has occurred here," he said.
"But [we need to] establish all facts first in a calm and considered way respond as appropriate."
Before the briefing Mr Rudd travelled to Brisbane to film an episode of the ABC's Kitchen Cabinet at his home.
Responding to a Sunday Telegraph article on the timing of the filming, Labor released a statement denying the briefing had been delayed for the filming commitment.
"Inference that the timing of Saturday evening's national security briefing to the Prime Minister on Syria has in any way been delayed because of other Prime Ministerial commitments in Brisbane is 100 per cent wrong and is defamatory," the statement said.
The Sunday Telegraph published a statement online saying it simply reported the timing of the events.
International community under mounting pressure to act
The White House says Mr Obama on Saturday received a "detailed review of a range of potential options" from his top advisers on how the United States and its allies could respond to an alleged chemical weapons attack.
Mr Obama, who is under pressure to act, also spoke with British prime minister David Cameron about Syria and agreed to consult about "potential responses by the international community," the White House said.
"The president has directed the intelligence community to gather facts and evidence so that we can determine what occurred in Syria," a White House official said.
"Once we ascertain the facts, the president will make an informed decision about how to respond."
French foreign minister Laurent Fabius, during a visit to the West Bank on Saturday, blamed Syria for a "chemical massacre" and said "the Bashar regime is responsible".
Russia is urging Damascus to cooperate with the UN but has dismissed calls for use of force against its ally.
Syrian ally Iran blamed the rebels and warned the West against any military intervention.
"There is proof terrorist groups carried out this action," foreign ministry spokesman Abbas Araqchi said, without giving any details.
Warning against any Western military intervention in the conflict, Mr Araqchi said "there is no international authorisation for" such action.
The UN says more than 100,000 people have been killed in Syria since an uprising against president Bashar al-Assad's rule flared in March 2011, while millions more have fled the country or been internally displaced.
Mr Ban is determined to "conduct a thorough, impartial and prompt investigation" into the chemical attack claims, his spokesman said.
Mr Ban has said the use of chemical weapons in Syria would constitute a "crime against humanity" that would reap "serious consequences".