Lawyers for US basketball star Brittney Griner on Monday filed an appeal against her nine-year prison sentence for drugs possession, Russian news agencies reported.

Griner, a centre for the Phoenix Mercury and a two-time Olympic gold medallist, was convicted on August 4.

She was arrested in February at Moscow’s Sheremetyevo Airport after vape canisters containing cannabis oil were found in her luggage.

Griner played for a women’s basketball team in Yekaterinburg during the WNBA off-season.

Lawyer Maria Blagovolina was quoted by Russian news agencies on Monday as saying the appeal was filed, but the grounds of the appeal were not clear.

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WNBA star and two-time Olympic gold medallist Brittney Griner (Evgenia Novozhenina/Pool/AP)

Blagovolina and co-counsel Alexander Boykov said after the conviction that the sentence was excessive and that in similar cases defendants have received an average sentence of about five years, with about a third of them granted parole.

Griner admitted that she had the canisters in her luggage, but said she had inadvertently packed them in haste and that she had no criminal intent.

Her defence team presented written statements that she had been prescribed cannabis to treat pain.

Before her conviction, the US State Department declared Griner to be “wrongfully detained”.

Secretary of state Antony Blinken took the unusual step of disclosing publicly in July that the US had made a “substantial proposal” to get Griner home, along with Paul Whelan, an American serving a 16-year sentence in Russia for espionage.

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Brittney Griner was jailed in Russia (Alexander Zemlianichenko/AP)

He did not elaborate, but the AP and other news organisations have reported that the US has offered to free Viktor Bout, a Russian arms dealer who is serving a 25-year sentence in the US and once earned the nickname the “Merchant of Death”.

On Sunday, a senior Russian diplomat said exchange talks have been conducted.

“This quite sensitive issue of the swap of convicted Russian and US citizens is being discussed through the channels defined by our presidents.

“These individuals are, indeed, being discussed.

“The Russian side has long been seeking the release of Viktor Bout.

“The details should be left to professionals, proceeding from the ‘do not harm’ principle,” Alexander Darchiev, head of the foreign ministry’s North America department, told state news agency Tass.