CARACAS, Venezuela — Venezuela's chief prosecutor said she has asked a court to freeze the assets of the editor of one of the country's two major opposition newspapers. El Nacional editor Miguel Henrique Otero called the move an attack on freedom of expression in statements published Sunday.

Chief Prosecutor Luisa Ortega Diaz said the case stems from an illegal-enrichment investigation against former Caracas Mayor Alfredo Pena. The mayor had sued Otero, alleging he owes him $3.5 million. Ortega said she doesn't know where the ex-mayor got the money or what the loan was for, but she said her office will investigate possible criminal activity, according to a statement posted on her agency's website.

If granted, the action would freeze Otero's bank accounts and block him from selling or disposing of his property.

Otero published a statement Sunday on the newspaper's website saying the action was "an outrage to limit freedom of expression." But he said he could not comment about the allegations because he had not been officially notified of them. He said he learned about the action only because friends told him that Ortega had issued a Twitter message announcing it.

Venezuela's last remaining opposition TV station, Globovision, was recently bought by businessmen friendly with the government, and the sharply critical private channel RCTV was kicked off the airwaves in 2007 when the government refused to renew its license.

Otero said government officials have systematically tried to dominate the news media by closing some outlets, and pushing others to self-censorship with criminal investigations.