Blasts shake Damascus as US and allies launch Syria strikes

The United States, Britain and France carried out a wave of pre-dawn strikes against Syria's regime today in response to a suspected chemical weapons attack, lighting up the sky of Damascus as explosions shook the city.

Branding last week's alleged gas attack the "crimes of a monster", US President Donald Trump announced the action against President Bashar al-Assad's regime in a White House address, defying fierce warnings from Damascus ally Russia.

A few minutes later, an AFP correspondent in Damascus heard a series of huge blasts and residents rushed to their balconies. For around 45 minutes, explosions echoed and the sound of warplanes roared over the city, as flashes flared in the distance.

When dawn broke, plumes of smoke could be seen rising from the city's north and east.

In the biggest foreign military action so far against Syria's regime, Western officials said a barrage of cruise and air-to-land missiles hit what they said were sites linked to chemical weapons development.

The targets included a scientific research facility in the Damascus area, a chemical weapons storage facility west of the city of Homs and a third location near Homs that contained both a command post and a chemical weapons equipment storage facility, the US military said.

But while Trump's belligerent tweets this week seemed to raise the prospect of large-scale military action, Saturday's strikes were narrowly targeted and the facilities hit had reportedly been evacuated in recent days.

Syrian state media reported only three people injured and Russia's defence ministry said there were "no victims" among Syrian civilians and military personnel.

Trump said the strikes were a direct response to an alleged April 7 chemical attack on the rebel-held town of Douma that rescuers and monitors say killed more than 40 people.

"The evil and the despicable attack left mothers and fathers, infants and children thrashing in pain and gasping for air. These are not the actions of a man. They are crimes of a monster instead," Trump said.

US Defence Secretary Jim Mattis called the strikes a "one-time shot" with no additional military action planned for now.

Assad, who has denied ever using chemical weapons and regularly denounces his opponents as "terrorists", responded to the strikes with a defiant vow.

"This aggression will only make Syria and its people more determined to keep fighting and crushing terrorism in every inch of the country," he said in comments published by his office.

Russia denounced the strikes as "aggressive actions" and called an emergency session of the UN Security Council.

Assad's other key ally Iran also denounced the attack, with supreme leader Ayatollah Ali Khamenei describing Western leaders as "criminals".

The targets appeared to steer well clear of any Russian personnel or equipment in Syria, where Moscow launched a military intervention in support of Assad in 2015.

The Russian military said the allies had fired 103 cruise missiles but that Syrian air defence systems managed to intercept 71 of them.

At a rally in central Damascus, 48-year-old Nedher Hammoud claimed to have seen missiles "being shot down like flies".

"Let them do what they want, kill who they want... History will record that Syria shot down missiles -- and not just missiles. It shot down American arrogance."