Claims that the Syrian government had used chemical weapons against its own people have been proved correct beyond doubt, thanks to previously undisclosed intelligence information including satellite images and intercepted communications, reports said.

While Syria's government, led by President Bashar al-Assad, has strongly denied the claims, one crucial piece of evidence about the use of chemical weapons, according to a Wall Street Journal report, came from Israeli spy services, which showed that several types of chemical weapons were moved in advance to the same Damascus suburbs where the attack took place a week ago.

Wednesday’s attack in Damascus’ suburb of Ghouta, which claimed 3,000 lives has evinced a strong reaction from various governments with UK Prime Minister David Cameron saying that the world could "not stand idly by," and France's President Francois Hollande stating that it was "ready to punish" whoever was behind the attack, according to BBC.

Steffen Seibert, a spokesman for German Chancellor Angela Merkel, said the chemical attack "is a serious breach of the international convention, which categorically bans the use of these weapons. It must be punished; it cannot remain without consequences," BBC reported.

The U.S., which is preparing to attack Syria if necessary, plans to make public some of the evidence before it takes any military action, reports said.

U.S. Vice President Joe Biden, too, said in a speech to a veterans’ group in Houston recently that there was "no doubt who was responsible for this heinous use of chemical weapons in Syria: the Syrian regime. Those who use chemical weapons against defenceless men, women, and children... must be held accountable," he added, according to BBC.

This is a marked shift in tone from U.S. officials who had initially highlighted the dangers of intervening with force in Syria without the approval of the U.N. Security Council, the Journal reported. 

The administration’s stand was reversed after the latest intelligence reports showed that the Syrian president had approved the use of chemical weapons and that the Syrian government was trying to cover up evidence of it, according to the Journal.

In the meantime, Russia and Iran sounded off warnings to the U.S. and its allies against launching a military attack on Syria, saying such an action would plunge the whole region into turmoil.

"Attempts to bypass the Security Council, once again to create artificial groundless excuses for a military intervention in the region are fraught with new suffering in Syria and catastrophic consequences for other countries of the Middle East and North Africa," the Russian Foreign Ministry said on Tuesday, according to Al Jazeera.

Abbas Araqchi, Iran's foreign ministry spokesperson, warned: “There will definitely be perilous consequences for the region."

Paul Rogers, a security analyst for Oxford Research Group, a London-based think tank, told Deutsche Welle: "Once you get any kind of action like this, it's far less easy to predict what will happen then."

"In the wider Middle East, even if it's a symbolic raid, it will be seen as one more example of the West interfering," Rogers added.

Reflecting on President Barack Obama's Middle East foreign policy, Arshin Adib-Moghaddam, a reader in International Relations at the University of London, said that while an attack on Syria would not affect Obama's popularity in the U.S. significantly, "it would make it that much more difficult to engage Iran," according to Deutsche Welle.

"A war against Syria would be another great strategic folly," he said.