US President Donald Trump has urged Florida election officials to abandon recount efforts, declare his fellow Republicans the winners and, without evidence, cast doubt on vote tallies as state officials scramble to review more than 8 million ballots by a Thursday deadline.

Key points: Mr Trump's call came despite rules allowing 10 days for absentee ballots

Mr Trump's call came despite rules allowing 10 days for absentee ballots Candidates have filed multiple lawsuits over closely watched Florida contest

Candidates have filed multiple lawsuits over closely watched Florida contest Several races in Florida and elsewhere remain too close to call

Leads by the Republican candidates in two key contested races — one for a seat in the US Senate and one for the governor's office — shrank as more ballots were tallied following last Tuesday's election.

Mr Trump's call to end the recount, which is mandated by Florida law because of the closeness of the races, came even though state rules allow election officials to wait 10 days for absentee ballots submitted by registered voters living outside the US, including active-duty military personnel.

"The Florida Election should be called in favor of Rick Scott and Ron DeSantis in that large numbers of new ballots showed up out of nowhere, and many ballots are missing or forged," Mr Trump tweeted.

"An honest vote count is no longer possible-ballots massively infected. Must go with Election Night!"

Mr Trump had previously accused Democrats of trying to "steal" the elections in Florida.

Over the weekend, a machine recount began in the race between outgoing Republican Florida Governor Rick Scott and incumbent Democratic US Senator Bill Nelson, with another recount underway for the Florida gubernatorial race between Republican Ron DeSantis and Democrat Andrew Gillum.

A supporter of Republican Senate candidate Rick Scott crosses her fingers at an election watch party. ( AP: Wilfredo Lee )

Mr Gillum shot back at Mr Trump on Twitter, saying: "You sound nervous. #CountEveryVote."

Republicans are eager to cement victories in a key battleground state after maintaining their control of the US Senate in last week's midterm congressional elections, while Democrats are eyeing another possible state governorship win. Both parties accused the other of trying to subvert democracy.

Mr Scott has filed a number of lawsuits over the recounts amid ongoing election drama echoing Florida's dramatic role in the 2000 US presidential vote recount. On Sunday, Mr Scott asked a judge to order police to impound voting machines and ballots when not in use.

Mr Nelson has also filed a federal lawsuit.

Mr Trump, whose Mar-a-Lago resort is located in West Palm Beach, complained about the Florida races in an early morning post on Twitter.

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Studies have found no evidence of large-scale voter fraud in the United States, although through the nation's history, courts have found evidence of policies intended to suppress voting by minorities.

The Florida Department of Law Enforcement, which has said it will review allegations of criminal fraud, said it had no active investigations as of late Friday.

Separately, neighbouring Georgia's gubernatorial race is also undecided, as is the Senate contest in Arizona.

Several House of Representative races also remain too close to call. Democrats seized control of the House in last week's election.

Reuters