A Russian court on Thursday sentenced US basketball star Brittney Griner to nine years in prison after she was found guilty of smuggling and storing narcotics.

Griner will spend a "total of nine years" in a Russian penal colony", judge Anna Sotnikova told the court, adding that the 31-year-old athlete will also have to pay a fine of 1 million rubles.

President Joe Biden, in response, called the sentencing "unacceptable".

"Russia is wrongfully detaining Brittney. It's unacceptable and I call on Russia to release her immediately so she can be with her wife, loved ones, friends and teammates," Biden said in a statement.

The US president reiterated that he would "work tirelessly and pursue every possible avenue" to repatriate Griner and another detained American in Russian, Paul Whelan. Negotiations are reportedly underway to swap the two for Russians incarcerated in the United States, including the notorious arms smuggler Viktor Bout.

The basketball star's defence team said it will appeal the verdict.

"The court completely ignored all the evidence of the defence, and most importantly, the guilty plea," the defence team said in a statement.

"The verdict is absolutely unreasonable. We will certainly file an appeal." (AFP)