US missiles sent in reprisal for a suspected chemical attack in Idlib has damaged around 20% of Syria's aircraft, US Defence Secretary James Mattis said.

The "measured response" by the US had resulted in the destruction of fuel and ammunition sites as well as air defence capabilities, Mattis added.

He continued: "The Syrian government has lost the ability to refuel or rearm aircraft at Shayrat airfield and at this point, use of the runway is of idle military interest."

Syrian military officials said significant materal damage was done but a spokesman for the Russian defence ministry played down the destruction inflicted by the US missile strike, according to BBC News.

A spokesperson for Russia said only six Syrian Air Force MiG-23s, and a few buildings, were destroyed, with only 23 of the missiles reaching the Shayrat airbase.

However, Mattis dismissed the claims in strident terms, saying that the US would "not passively stand by while [Syrian President Bashar al-Assad] murders innocent people with chemical weapons".

Further strikes against Syria have not been ruled out according to White House Press Secretary Sean Spicer.

"The sight of people being gassed and blown away by barrel bombs ensures that if we see this kind of action again, we hold open the possibility of future action," he said.

Syria chemical attack
Syrian children receive treatment following a suspected toxic gas attack in Khan Sheikhun, a rebel-held town in the northwestern Idlib province Mohamed al-Bakour/AFP

The strike will have the effect of weakening the overall air defence and ground attack capabilities of the (Syrian air force), said analyst Reed Foster of the defence and intelligence publication Jane's. But "it will not significantly diminish the ability of the Assad regime to conduct further chemical weapons attacks,"

According to the Syrian Observatory for Human Rights, two Syrian jets took off on Friday (7 April) from the air base attacked by the US missiles. Air strikes were carried out on areas under Islamic State (Isis) control in the eastern Homs province.

The Syrian government has repeatedly denied involvement in the chemical attack unleashed on the rebel-held town of Khan Sheikhoun on Tuesday (4 April) that killed 89 people.