Iranian authorities have moved to limit Internet access ahead of expected anti-government protests to deny the opposition a vital means of communication, Teheran residents said Sunday. They said they were unable to access e-mail and that the government's blockage of opposition Web sites has been tightened. It was not immediately clear whether the blockage was nationwide or limited to Teheran. Separately, authorities have told journalists working for foreign media organizations not to leave their offices to cover the street protests expected Monday. December 7 is a traditional day for rallies marking the killing of three students during a 1953 anti-US protest. It has served as a day for pro-reform protests since the 1990s.