* Ex-PM Abdullojonov detained after flying in from U.S.
* Was accused over 1997 attempt on Tajik leader
* Ukraine mulls his extradition to Tajikistan
KIEV, Feb 6 (Reuters) - Ukrainian police have detained a former prime minister of Tajikistan, authorities said on Wednesday, years after he was accused of being behind a assassination attempt on veteran Tajik leader Imomali Rakhmon.
Authorities in the Tajik capital Dushanbe said Abdulmalik Abdullojonov, 64, was held on Tuesday after arriving at Kiev's Borispil airport on a flight from the United States where he has lived since 1998.
Abdullojonov has long denied accusations by Tajik officials that was he was involved in an attempt on the life of his political rival Rakhmon in 1997.
Ukrainian police confirmed the arrest of a 64-year-old man who was wanted by Tajik authorities for "very serious crimes". "The question of his extradition is now being decided," a statement by the Ukrainian police said.
Abdullojonov, prime minister from 1992-3 soon after the Central Asian state's independence from the Soviet Union, could face up to 20 years in prison in Tajikistan, the statement added.
Tajik police said Abdullojonov, who ran unsuccessfully against Rakhmon for president in 1994 and then left the country, had been detained by the Ukrainian authorities "at our request".
He is wanted on suspicion of activities aimed at carrying out a seizure of power in Tajikistan, a Tajik police source told Reuters.
"He has been on the wanted list for 16 years. We very much hope that the Ukrainian authorities will take into account the irrefutable evidence gathered on Abdullojonov," he said.
The source did not give details of the charges against the former premier.
But in April 1997, Rakhmon was wounded in the leg in an attempt on his life while he was visiting Khujand in the north, a power base of Abdullojonov. Authorities later named Abdullojonov, who was not in the country at the time, as the organiser of the assassination attempt.
Predominantly Muslim Tajikistan, which lies on a major transit route for Afghan drugs to Europe and Russia, remains volatile after a 1992-97 civil war in which Rakhmon's Moscow-backed secular government clashed with Islamist guerrillas.
Rights groups have accuised Rakhmon of cracking down on dissent and blocking websites before a November election that could extend his two-decade rule.
Rakhmon, who has been in power since 1992 in the mountainous state which borders Afghanistan and China, brought Abdullojonov into the government in the early days of independence as a concession to the north of country where his rival came from.
But Rakhmon very soon sought to sideline him and sent him to Moscow as ambassador from where Abdullojonov staged his unsuccessful bid for the presidency. In 1998, Abdullojonov left to live in the United States. (Writing By Richard Balmforth; Editing by Andrew Heavens)