US election officials have rejected President Donald Trump’s claims of electoral fraud, declaring on Thursday that the White House vote was “the most secure in American history.”

“There is no evidence that any voting system deleted or lost votes, changed votes or was in any way compromised,” said a statement from the Department of Homeland Security’s cybersecurity and infrastructure security agency (Cisa).

Mr Trump is stubbornly refusing to concede to Democratic president-elect Joe Biden, insisting that 2.7 million votes for him  in last week’s poll were deleted.

His claims of widespread fraud remain unsubstantiated but Mr Trump has lodged a series of legal challenges in a bid to overturn the result.

Despite most analysts believing the lawsuits will fail, his campaign received a boost earlier this week when Attorney-General William Barr, a known Trump loyalist, ordered district attorneys to investigate claims of fraud.

As counting continues, Mr Biden has been projected as the winner of Arizona, granting him 11 more electoral-college votes. It is the first time the state has voted Democrat since 1996.

The Cisa statement said: "While we know there are many unfounded claims and opportunities for misinformation about the process of our elections, we can assure you we have the utmost confidence in the security and integrity of our elections, and you should too.

“When you have questions, turn to elections officials as trusted voices as they administer elections.”

Cisa director Christopher Klebs said that he expects Mr Trump to sack him following the statement.

Assistant director Bryan Ware resigned on Thursday, complying with a White House demand issued earlier this week.