Updated

An 18-year-old opposition demonstrator accused of assaulting police was put under house arrest on Tuesday by a Moscow court amid a widening official probe into an opposition rally that ended in clashes, officials said.

Moscow student Alexandra Dukhanina was detained earlier this week on charges of violence against authorities and calling for riots. The Basmanny District Court ordered her to remain under house arrest pending an investigation.

The photos of a burly police officer dragging Dukhanina by the neck during the May 6 protest in central Moscow featured prominently on Russian news sites and the blogosphere, fueling anger against the police crackdown on the rally.

The demonstration of at least 20,000 people the day before President Vladimir Putin's May 7 inauguration turned into a fierce battle with police after some protesters tried to march on the Kremlin. Some in the crowd started hurling stones at police, who fought back with clubs and tear gas. Dozens were injured in the clashes and hundreds were arrested.

Some opposition activists have claimed that the violence was incited by unknown provocateurs.

A video posted on Russian news sites showed a woman identified as Dukhanina picking up a piece of asphalt and hurling it in the direction of police. It wasn't clear from the video whether she hit anyone. Dukhanina's lawyer said she had admitted attending the protest but denied the official charges.

Investigators said that another two suspects accused of violence against police were detained Monday, and police were searching for other suspects.