By Katharine Mieszkowski: Amid the protests after the disputed Iranian presidential election, many foreign journalist's visas are expiring, and the government is refusing to renew them.

Loren Jenkins, the senior foreign editor for National Public Radio, said: "I think they want everyone out of there so they can crack down," according to the New York Times' Media Decoder blog.

Bill Keller, the executive editor of the New York Times, who planned to leave Tehran on Wednesday when his visa was set to expire, wrote in an e-mail: "Visa extensions have been denied across the board."

It's common for many foreign journalist's visas in Iran to only last a week, and this is clearly not a time when the government is inclined to make an exception.

Jim Sciutto, an ABC News correspondent in Tehran, wrote on Twitter Tuesday that "Iran has banned all foreign journalists from reporting on the sts." Many Western journalists were effectively confined to their offices or hotel rooms on Tuesday after authorities forbid them from reporting on protests or conducting interviews outside. Some were threatened with arrest for filming protests.

Some outlets, such as the New York Times, NBC and the Associated Press, also employ Iranian journalists, who will continue reporting. Salon has published freelance reports from Iranians under anonymous or pseudonymous bylines to protect them from government reprisal. A few outlets even have year-round bureaus in the country, which will continue to operate.

But the international media crackdown suggests that eyewitness accounts by Iranians posted online will increasingly be telling the story to the rest of the world in the days to come.