Pentagon officials said that three different sites had been targeted in the attacks.

Secretary of Defense James Mattis told reporters there were no reports of losses in the operation, saying "Right now, this is a one-time shot, and I believe it has sent a very strong message."

Anatoly Antonov, the Russian ambassador to the US, has responded to the air strikes in Damascus and Homs. He says Moscow’s warnings have been left unheard and that Russia is being threatened. “We warned that such actions will not be left without consequences,” he says.

He says “insulting the president of Russia is unacceptable and inadmissible” and that the US, as a holder of chemical weapons, has no moral right to blame other countries.

The World Health Organization said on Wednesday that an estimated 500 patients went to health facilities with “signs and symptoms consistent with exposure to toxic chemicals” during a suspected chemical attack in Douma last weekend.

More than 70 people sheltering in basements have reportedly died, with 43 of those deaths related to symptoms consistent with exposure to highly toxic chemicals, WHO said. Two health facilities were also affected by the attacks, it added.

Reporter’s code: 50101