President Bashar al-Assad is telling Donald Trump "F you" by flying warplanes from the Syrian air base targeted by US cruise missiles, Senator Lindsey Graham has said.

Syrian jets reportedly took off from the Shayrat air base less than 24 hours after it was pounded by 59 Tomahawk cruise missiles.

Mr Trump ordered the strikes on the base in retaliation for the chemical weapons attack on Khan Sheikhoun.

"We do have treaties that we've signed all over the world saying that we're not going to let one nation use weapons of mass destruction, that's what the chemical weapons treaty is all about," Mr Graham told NBC's Meet the Press.

"But I will say this, if you kill babies with conventional bombs it's still a moral outrage."

In pictures: US missile strike against Syria Show all 7 1 /7 In pictures: US missile strike against Syria In pictures: US missile strike against Syria The guided-missile destroyer USS Porter (DDG 78) launches a tomahawk land attack missile in the Mediterranean Sea AP In pictures: US missile strike against Syria The United States military launched at least 50 tomahawk cruise missiles at al-Shayrat military airfield near Homs, Syria, in response to the Syrian military's alleged use of chemical weapons in an airstrike in a rebel held area in Idlib province EPA In pictures: US missile strike against Syria Shayrat airfield in Syria Getty Images In pictures: US missile strike against Syria US Navy guided-missile destroyer USS Ross (DDG 71) fires a tomahawk land attack missile in Mediterranean Sea Reuters In pictures: US missile strike against Syria US Navy guided-missile destroyer USS Ross (DDG 71) fires a tomahawk land attack missile in Mediterranean Sea Reuters In pictures: US missile strike against Syria President Donald Trump speaks at Mar-a-Lago in Palm Beach, Fla., after the US fired a barrage of cruise missiles into Syria in retaliation for this week's gruesome chemical weapons attack against civilians AP In pictures: US missile strike against Syria Syria's President Bashar al-Assad Reuters

He added: "Here's what I think Assad's telling Trump by flying from this base: 'F you.'

"And I think he's making a serious mistake, because if you're an adversary of the United States and you don't worry about what Trump may do on any given day, then you're crazy."

During the interview, Mr Graham also said he believed that Mr Trump didn't need to consult with Congress to carry out the strike.