Russia's ousted defence minister is to be questioned by investigators as part of a probe into multimillion dollar embezzlement by his former employee, an official said Thursday.

Anatoly Serdyukov, who was sacked by President Vladimir Putin last month over a corruption scandal in his ministry, has been summoned to the Investigative Committee for questioning, the committee's spokesman Vladimir Markin told Russian news agencies.

Markin said the summons was for Friday. Serdyukov's lawyer Genrikh Padva said investigators had already held an initial meeting with Serdyukov, the Interfax news agency reported.

Putin explained the dismissal of a top minister by the need for a thorough investigation into a suspected $100 million property scam at a defence ministry holding company, which was headed by a 33-year-old woman rumoured to be the minister's mistress.

The woman, Yevgenia Vasilyeva, has been placed on house arrest in her luxurious apartment.

Serdyukov had not been charged with any crime however, and Thursday was the first time investigators mentioned him as a part of the graft probe, following media reports that the ex-minister had left the country.

His lawyer dismissed such allegations, saying Serdyukov has been in Moscow.