(CNN) -- Iranian authorities have blocked the word "Bahman" -- the 11th month of the Persian calendar -- from Internet searches within the country, according to an opposition website.
The measure appears to be an effort by Iranian authorities to obstruct access to several websites that are promoting a rally on Monday -- the 25th day of Bahman -- proposed by Iranian opposition leaders in support of the uprising in Egypt, Saham News reported Saturday.
Two Tehran residents also confirmed the block via e-mail to CNN.
Iranian authorities on Wednesday warned against any attempt by the opposition movement to hold the rally, according to the state-run Islamic Republic News Agency.
"We definitely see them as enemies of the revolution and spies, and we will confront them with force," Revolutionary Guard Cmdr. Hossein Hamedani told IRNA.
The White House issued a statement Saturday condemning the Iranian government for attempting to block the protests.
"By announcing that they will not allow opposition protests, the Iranian government has declared illegal for Iranians what it claimed was noble for Egyptians," National Security Advisor Tom Donilon said in the statement. "We call on the government of Iran to allow the Iranian people the universal right to peacefully assemble, demonstrate and communicate that's being exercised in Cairo."
Following the resignation Friday of Egyptian President Hosni Mubarak, the head of Iran's National Security Council, among other Iranian authorities, lauded the leader's toppling, comparing "the Egyptian Revolution with the victory of Iran's Islamic Revolution," according to Iran's state-run media.
But while publicly praising the Egyptian uprising, the Iranian government has rounded up activists after Iran's two leading opposition figures called for Monday's rally.
Opposition leaders Mehdi Karroubi and Mir Hossein Moussavi asked that the rally take place in Tehran's Azadi Square, the site of mass protests by Iran's opposition movement after the disputed 2009 presidential elections.
The International Campaign for Human Rights in Iran, based in the United States, called Friday for an end to restrictions on the movements of Karroubi and Moussavi.
"The (Iranian) government is doing all it can to intimidate Iranians and deny their right to peaceful assembly," the U.S.-based group said in a statement. "With recent events in Egypt, we see another round of repression in Iran aimed at silencing a people frustrated and dissatisfied by the denial of their human rights."