The US is concerned Moscow may have "tampered" with evidence

Russia has told chemical weapons experts they'll be allowed to visit the site of a poison gas attack on Wednesday.

The US has voiced concerns though that Moscow may have already "tampered" with evidence in Douma where more than 40 people died.

It's as Syrian state television claims air bases in Homs have come under attack from missile strikes.

Peter Wilson from the Organisation for the Prohibition of Chemical Weapons (OPCW) says his fellow investigators just want the opportunity to report the truth.

"We are obviously keen to make sure that the inspectors have every means that they can to carry out their job and carry out their investigation as soon as possible.

"We see no reason why they should not be able to get to Douma".