The Syrian Observatory for Human Rights said a total of three scientific research centres had been hit in the attacks - two in Damascus and one in the Homs area - in addition to military bases in Damascus.

The UK’s Ministry of Defence said the strike against Syria on April 14 had been aimed at a military facility where the Syrian government was assessed to have stockpiled chemicals. Four Tornado jets had carried out the attack using Storm Shadow missiles on a military facility some 24 km west of Homs. "Very careful scientific analysis was applied to determine where best to target the Storm Shadows to maximise the destruction of the stockpiled chemicals and to minimise any risks of contamination to the surrounding area," the MoD said in a statement.

The US used Tomahawk cruise missiles in its strikes in Syria, and taking aim at multiple targets in the country, a US official said.

A witness said the Barzah district of Damascus had been hit in the strikes. Barzah is the location of a major Syrian scientific research centre.