NEW YORK—An Internet entrepreneur accused of being behind an online marketplace for illegal drugs has asked the government to return more than $30 million in bitcoin seized from his computers.

Ross Ulbricht, of San Francisco, was arrested in October following a crackdown on the black market website Silk Road.

Federal prosecutors in New York say Ulbricht went by the online handle, "the Dread Pirate Roberts," and turned the underground site into a place where anonymous users could buy or sell all sorts of contraband and illegal services.

In court filings, prosecutors said they seized 144,336 bitcoins from Ulbricht's computers.

The virtual currency is exceedingly valuable, but lightly regulated.

Ulbricht said in a legal filing on Dec. that the currency should be returned because it isn't subject to civil forfeiture rules.