He told Fox News the Democrats were putting out the reports because they were embarrassed at the scale of the election defeat.
On Friday, CIA officials told US media they had concluded that Russians hackers were trying to help Mr Trump.
Russian officials have repeatedly denied the hacking accusations.
Mr Trump said it might have been Russia but it was impossible to know.
"They have no idea if it's Russia or China or somebody sitting in a bed some place," he said.
