Iran has questioned claims by the US and its allies that the Syrian government has used chemical weapons.

The country's foreign minister, Mohammad Javad Zarif, said he has "serious doubts" over whether such allegations "can be verified".

He called for an investigative team to be deployed to perform chemical tests, questioning reports that such weapons were used in an attack on the Syrian town of Khan Sheikhoun in April.

Last month, a report by a chemical weapons watchdog confirmed that the nerve gas sarin was used in the attack, which left at least 86 people dead including 30 children.

US President Donald Trump ordered a surprise airstrike of cruise missiles on the Shayrat airbase just days after the 4 April attack.

Speaking at the Council on Foreign Relations in Washington DC on Monday night, Mr Zarif said: "We have serious doubts that the recent allegations by the United States about the use of chemical weapons against Khan Sheikoun can be verified.

"We suggested that they should send an investigative team to the region. We said that if chemical weapons have been used there are traces."

He continued: "You can find where they were used, how they were used, from which locality they were used and it would have been easy.

"It would have been easy for a team to go to Khan Sheikoun, and it would have been easy for a team to go to Shayrat airbase, because if they said they loaded the planes with chemical weapons at the Shayrat airbase, traces would remain. Nobody would be able to remove those traces."

The US later admitted that it could not say for certain whether or not chemical weapons were at the Shayrat airbase targeted in the strike.

Earlier this month, Edmond Mulet, the Head of the Joint Investigative Mechanism (JIM) on the use of chemical weapons in Syria, said it was an "indisputable fact" that chemical weapons have been used Syria.

He said people have died "because of such deadly and insidious weapons which the world found inhumane already more than 100 years ago."

Mr Mulet confirmed that the JIM was investigating the 4 April attack in Khan Sheikhoun and another incident which took place in September in Idlib.