A lawyer for a prominent Russian journalist detained on charges of drug dealing has filed a complaint with the country's top investigative body, saying police used violence against him while in custody.

Police have denied claims that Ivan Golunov was beaten after his arrest on Thursday.

His lawyers said he may have suffered a concussion and rib fractures. He was examined in hospital on Saturday and found to have abrasions on his back and a bruise around one eye.

Later on Saturday, a court released Golunov into house arrest.

Olga Dinze, a lawyer with the human rights group Agora, filed a statement with Russia's Investigative Committee saying Golunov was subjected to "unmotivated physical violence" by police.