Turkmen President Saparmurat Niyazov announced on Thursday the arrest of a leading opponent, Boris Shikhmuradov, who stands accused of masterminding a coup attempt last month.
Niyazov broke the news to diplomats outside his gold-domed presidential palace, its palm trees dusted with rare snow, as they awaited Pakistani and Afghan leaders who are to sign an important gas pipeline deal.
Presidential spokesman Serdar Durdiyev said Shikhmuradov, a former foreign minister, had been detained inside the Central Asian republic but gave no further details.
Turkmenistan's prosecutor general is due to make a brief statement on state television around 1600 GMT.
Shikhmuradov is the main suspect in a November 25 assassination attempt against Niyazov, whose motorcade was raked with machinegun gunfire as it travelled through central Ashgabat.
Niyazov escaped unhurt.
Shikmuradov was sent to China after eight years as foreign minister but in October 2001 was recalled to Ashgabat. He refused to return and instead moved to Moscow, where he became an outspoken critic of Niyazov. Widely referred to here as Turkmenbashi (Father of the Turkmen), Niyazov blamed the attack on an international network of mercenaries, including from Turkey and neighbouring Russia. Russia has tense relations with the former Soviet republic, and sees Niyazov as obstructing plans to share the vast mineral wealth of the Caspian Sea on their borders.
At the weekend Turkmenistan gave neighbouring Uzbekistan's ambassador 24 hours to leave, accusing him of aiding those allegedly behind the bid to kill Niyazov.
Like Uzbekistan, the largely desert Turkmenistan is a major cotton producer and disputes over rights to water in a river that forms their border have raised tensions.
Human rights activists say more than 100 people have been arrested following the botched assassination bid.