Voters in Tajikistan are casting ballots in a presidential election that is all but certain to extend the incumbent's rule after officials barred the only real opposition candidate from the race.

President Emomali Rakhmon, 61, is running for a fourth term in Wednesday's vote in the mountainous Muslim nation neighboring Afghanistan and China. Rakhmon has led the impoverished ex-Soviet country for more than two decades.

The remaining five challengers all have praised Rakhmon.

For many years, Rakhmon's government has cracked down on dissent and maintained tight control over the media, drawing harsh criticism from international rights groups.

The Tajik authorities have sought to exploit public fears of a replay of a bloody civil war in the 1990s, casting the opposition as a threat to the country's stability.