MOSCOW, December 27 (RIA Novosti) - A presidential candidate fielded by the Turkmen opposition has gone missing in Ashgabat, the United Democratic Opposition of Turkmenistan said in a statement Wednesday.

Former President Saparmurat Niyazov died of heart failure last Thursday at the age of 66. Turkmenistan's acting President Gurbanguly Berdymukhammedov was approved as presidential candidate by the Central Asian state's highest legislative body Tuesday along with five other contenders.

The opposition said Nurberdy Nurmammedov, chairman of the Agzybirlik People's Democratic Movement, disappeared in the republic's capital December 23 shortly after his interview on Radio Liberty where he said he hopes democracy will prevail in Turkmenistan.

The statement said the opposition believes Nurmammedov was arrested on orders from the Turkmen incumbent authorities, demanding his immediate release.

Turkmenistan's opposition earlier also nominated a former deputy prime minister as a presidential candidate.

An opposition spokesman said Khudaiberdy Orazov, the leader of the Vatan (Homeland) movement, currently living in Sweden, is "a real patriot," intolerant of the authoritarian regime and is capable of "reforming Turkmenistan into a modern democratic state with a developed economy."

Orazov, whom the Turkmen Prosecutor General's Office accuses of embezzlement, told a news conference in Kiev earlier that the opposition will seek democracy in Turkmenistan by all means, and that a revolution is not ruled out.

The People's Council, ruled Tuesday that the new presidential election will be held February 11.