Image copyright AP Image caption Sen Graham said Russia was trying to "destabilise democracy all over the world"

Senior US Republican senator Lindsey Graham has said his campaign email account was hacked by Russians.

Sen Graham also told CNN that he believed "the Russians" hacked into the Democratic National Committee, and accused them of trying to "destabilise democracy all over the world".

Officials in Russia have repeatedly denied hacking accusations.

President-elect Donald Trump rejected a CIA report that Russian hackers tried to sway the election in his favour.

In a separate development, NBC News reported that US intelligence officials now believe with "a high level of confidence" that Russian President Vladimir Putin became personally involved in a covert Russian campaign to interfere in November's presidential election.

The attack targeted emails of the Democratic Party and of John Podesta, a key aide to presidential nominee Hillary Clinton. The contents, passed to Wikileaks and posted online, were embarrassing to the Democrats and shook up the presidential campaign.

The NBC report, quoting two unnamed senior officials, says that new intelligence shows how the hacked material was leaked and used.

It added that the operation began as a "vendetta" against Mrs Clinton before becoming "an effort to show corruption in American politics and split off key American allies".

Mr Putin is said to have been furious when Mrs Clinton, as secretary of state, questioned the integrity of 2011 parliamentary elections in Russia. He publicly accused her of encouraging street protests.

The BBC has not been able to confirm the report.

Image copyright AP Image caption Hacking was seen as embarrassing to the Democrats and hit Mrs Clinton's presidential campaign

Sen Graham, a member of the powerful Senate Armed Services Committee, said on CNN that "we were told by the FBI in August that we were hacked in June".

"I do believe the Russians hacked into the [DNC]. I do believe they hacked into [John] Podesta's email account. They hacked into my campaign account," he said.

He also said that he believed that "all the information released publicly hurt Clinton and didn't hurt Trump."

But he stressed that the outcome of the election was not in doubt.

"I think Hillary Clinton lost because she wasn't an agent of change and she tried to disqualify Trump and she wasn't able to do it."

However, Sen Graham added that this was not "a Republican or Democratic issue" and must be tackled on a bipartisan basis.

He accused Russia of attempting to destabilise democracy.

"We should tell the Russians that on no uncertain terms, you interfere in our elections, we don't care why, we're going to hit you and hit you hard, we're going to introduce sanctions."