The first two sentences are perfect.
I don't think we would normally talk about an accusation being "attributed."
You would be far more likely to read a sentence such as this:
"The allegations levelled at us are untrue."
However, if the accusation was that somebody had said something controversial then you would read:
"The comments attributed to me are untrue."
For example, Prince Harry has been accused of saying that an enquiry into the behaviour of UK soliders "is a joke"
He has denied the comments. And Buckingham Palace has denied them. Buckingham Palace probably denied them by saying "The comments attributed by the media to HRH are untrue."
You can probably see the difference above:
If something is "attributed," then it belongs to somebody.. so the comments are attributed to somebody because comments made belong to the person that said them.
The accusation is not "attributed," because it does not belong to the person that was accused. Prince Harry does not own the accusation that was made about him.