The US has said it holds Russia (click here) responsible for a deadly attack on an aid convoy near the Syrian city of Aleppo on Monday.
The White House has called it an "enormous humanitarian tragedy".
Meanwhile, US officials have told the BBC that two Russian war planes were responsible for the attack.
Russia strongly denies involvement of its own or Syrian planes, and says the incident was caused by fire on the ground and not by an air strike.
"There are no craters and the exterior of the vehicles do not have the kind of damage consistent with blasts caused by bombs dropped from the air," a statement from the defence ministry said.
And the country's foreign ministry spokeswoman said the US government had "no facts" to support its claim, adding: "We have nothing to do with this situation."...
