Journalists have become a prime target in an Iranian government crackdown on the opposition following last June’s disputed presidential election, with 52 of them currently held — making Iran the top jailer of journalists in the world, according to the Committee to Protect Journalists.

The wave of arrests, which has only accelerated recently, has sent a chill through journalists in Iran at a time when the opposition is struggling to maintain its challenge against the government in the face of a heavy crackdown on pro-reform figures.

In response, a sort of ”underground” journalism has emerged, said Reza Valizadeh, 32, who used to work for the state-run radio and television but who fled the country amid the postelection crackdown.

”We have a kind of guerrilla journalists, who wear masks, have no names, write under pseudonyms and send e-mails without mentioning their real names to news outlets outside Iran, or publish in weblogs with pseudonyms,” said Valizadeh, who now lives in Paris.

”A very, very bitter and black period awaits journalists,” he told The Associated Press.

The at least 52 journalists now in Iranian jails range from freelance reporters to writers for opposition blogs and newspapers and even several for government-owned media, the New York-based Committee to Protect Journalists wrote in a report released Tuesday. Seven of them were imprisoned before the June election.