Oct 13 (Reuters) - A federal appeals court reinstated an order from Republican Texas Governor Greg Abbott that limits absentee ballot drop-off sites to only one per county, regardless of population or size, despite opposition from Democrats and voting rights advocates.

The 5th U.S. Circuit Court of Appeals late Monday put on hold a lower court ruling that had blocked Abbott's order from taking effect, finding it would not hinder Texans from exercising their right to vote.

The decision means more than a dozen satellite locations in at least two counties will remain shut down: Harris, which includes Houston and has more than 4 million residents, had set up 12 locations, while Travis, which includes Austin, had four.

Voting by mail, and early voting in general, is surging in this election, as voters seek to avoid waiting in lines at polling places amid the ongoing coronavirus pandemic. Nationally, more than 10 million votes have already been cast, a record-shattering pace, according to data compiled by the U.S. Elections Project.

President Donald Trump, a Republican, trails in most national polls behind his Democratic challenger, former Vice President Joe Biden.

Trump has repeatedly claimed without evidence that mail ballots will lead to fraud. Experts have dismissed that assertion, noting that mail voting is a longstanding feature of U.S. elections, which have historically seen virtually no voter fraud.

Republicans and Democrats have been engaged in a multistate legal battle over the rules governing mail-in ballots, including drop boxes.

Texas is one of the few states that does not allow all residents to vote by mail. Only voters who are over 65, away from home on Election Day, ill, disabled or in jail are permitted to cast absentee ballots.

In light of the pandemic, Abbott signed an order this summer allowing voters to submit absentee ballots ahead of Nov. 3's Election Day, a first for the state. But he subsequently issued a second proclamation limiting counties to a single drop-off site, citing the potential for fraud.

The appeals court said the two orders, taken together, represent an expansion, not a restriction, of the right to vote, since Texas typically allows voters to bring mail ballots in person only on Election Day.

"How this expansion of voting opportunities burdens anyone's right to vote is a mystery," the unanimous three-judge panel wrote. All three judges were nominated to the court by Trump.

In a Twitter post, Abbott wrote, "Critics were clearly clueless about the legality of my action and simply voiced prejudicial political opinions."

The state Democratic Party did not immediately respond to a request for comment.

In-person early voting in Texas starts on Tuesday.