A judge who lifted a gay marriage ban in Utah, one of the most conservative US states, has denied an application by officials to reverse the move.

Judge Robert Shelby's ruling on Friday that Utah's ban on same-sex nuptials was unconstitutional has dismayed the Republican governor and Mormon church.

He has now denied state lawyers' bid to suspend his ruling pending an appeal.

Hundreds of gay couples have been tying the knot in several counties where marriage licences are being issued.

The state asked the 10th Circuit Court of Appeals in Denver to grant an emergency stay that would have immediately stopped gay weddings until the court can rule on whether last week's decision was valid.

Judge Shelby himself heard Monday's challenge, and rejected it.