The announcement of Ambassador Volodymyr Yelchenko's dismissal was made today by presidential aide Oleksandr Chaliy.
He said the move was linked to Yelchenko's purported decision to issue an entry visa for exiled Turkmen opposition leader Khudaiberdy Orazov.
"The president behaved with severity, [but] he had no other choice," Chaliy said. "He made a decision that could stabilize our relations with Turkmenistan. We expect similar actions from the Ukrainian government. The president expects similar actions [from the government]."
It is unclear when Yushchenko's decision comes into force.
Chaliy says the presidential decree will be published "after Yelchenko completes his diplomatic mission" in Vienna.
Last week, Ukrainian media reported that Orazov and another exiled Turkmen opposition leader, Nurmukhammed Khanamov, visited Kyiv after the death of Turkmen President Suparmurat Niyazov in December on the official invitation of Ukrainian Transportation Minister Mykola Rudkovskiy.
Rudkovskiy denies those reports.
Chaliy today said Yushchenko is expecting the government -- which is headed by bitter political rival Viktor Yanukovych -- to sack Rudkovskiy.
Ukraine depends on Turkmen gas imports for its energy needs and has been maintaining good ties with Ashgabat, which is at a crucial junction following the death of long-time leader Niyazov.
Yushchenko and Yanukovych are in a dispute over the president's prerogatives and his appointment as foreign minister, Borys Tarasyuk.
(with additional reporting by Unian, Interfax-Ukrayna, and "Ukrayinska Pravda")