US President Donald Trump said on Thursday he ordered a targeted military strike on the airfield in Syria from which a deadly chemical attack was launched and added there could be no dispute that Syria had used banned chemical weapons.

“It is in the vital national security interest of the United States to prevent and deter the spread and use of deadly chemical weapons,” Trump said.

“There can be no dispute that Syria used banned chemical weapons, violated its obligations under the chemical weapons convention and ignored the urging of the UN Security Council.”

A White House official said 59 precision-guided missiles hit Shayrat Airfield in Syria, where the US believes Tuesday's deadly attack was launched. The official had earlier given the number of missiles involved as 70.

The missiles were blasted from the USS Porter and the USS Ross, which belong to the US Navy's Sixth Fleet and are located in the eastern Mediterranean. A US official said the missiles targeted aircraft and runways at the base.

“This site was associated with the Syrian regime's chemical weapons program and directly linked to the horrific chemical weapons attack April 4th,” the White House official said.

“We assess with a high degree of confidence that the chemical weapons attack earlier this week was launched from this site by air assets under the command of the Assad regime,” the official added.

“We also assess, with a similar degree of confidence, that the Assad regime used a chemical nerve agent consistent with sarin in these attacks.” Inhaled or absorbed through the skin, sarin gas kills by crippling the respiratory centre of the central nervous system and paralyses the muscles around the lungs.

Sarin was used by Iraqi dictator Saddam Hussein's regime to gas thousands of Kurds in the northern town of Halabja in 1988.

The UN Security Council failed Thursday to reach agreement on demands for a thorough investigation of the strike in northwestern Syria's Khan Sheikhun, in which at least 86 people, including 27 children, died. AFP/REUTERS