TEHRAN, IRAN - Iran's ruling clerics closed ranks around President Mahmoud Ahmadinejad on Tuesday, hailing him as a "champion" amid signs that he may have begun purging his government of people perceived to be opposition sympathizers.

A sense of resignation mingled with indignation settled over supporters of opposition leader Mir Hossein Mousavi, whose claim that massive fraud robbed him of victory in the June 12 presidential election touched off two weeks of violent street clashes.

Iran's highest electoral authority, the Guardian Council, proclaimed the election outcome valid Monday -- paving the way for Ahmadinejad to be sworn in next month -- and the president sent a stern message to those in his administration who survived his first term: He won't tolerate dissent in his second.

Three senior Oil Ministry officials with loose ties to Mousavi were fired, the independent news agency Fararu reported.

Ahmadinejad gave a speech at the Intelligence Ministry before embarking on a trip today to Libya to attend a meeting of African leaders.

"The overt and covert conspiracies of enemies for soft regime change in Iran were defeated," the pro-government Fars news agency quoted him as saying. He also called on Iranians to use all means "to break the monopoly of the global powers."

Ahmadinejad basked in the praise of ranking clerics.

Ayatollah Muhammad Ali Taskhiri was quoted as saying in a congratulatory message that Ahmadinejad has been "a champion, always on the scene." Another top cleric, Ayatollah Mohammad Yazdi, said the election was "the cleanest ever" in the history of the Islamic Republic.

In Qom, the Shiite holy city that is a base for leading clerics, Ayatollah Morteza Moghtadai, the influential head of a seminary, decreed that "opposing the view of the Guardian Council is not legal, religious or socially acceptable."

In a sign of the growing restrictiveness, authorities presented to local news media a detained Canadian-Iranian filmmaker and Newsweek correspondent, Maziar Bahari, who described Western journalists in Iran as spies.

The Associated Press and Washington Post contributed to this report.