CAIRO -- Egypt's chief prosecutor ordered an investigation Thursday into allegations that opposition leaders committed treason by inciting supporters to overthrow Islamist President Mohammed Morsi.
The probe by a Morsi-appointed prosecutor was launched a day after the president called for a dialogue with the opposition to heal rifts opened in the bitter fight over an Islamist-drafted constitution just approved in a referendum. The opposition decried the investigation as a throwback to Hosni Mubarak's regime, when the law was used to smear and silence opponents.
The probe was almost certain to sour the already-tense political atmosphere in the country.
The allegations were made initially in a complaint by at least two lawyers sent to the chief prosecutor earlier this month. They targeted opposition leaders Mohammed ElBaradei, a Nobel Peace laureate and former head of the U.N. nuclear agency; former Foreign Minister Amr Moussa; and Hamdeen Sabahi. Both Mr. Moussa and Mr. Sabahi were presidential candidates who competed against Mr. Morsi in the last election.
There was no immediate comment by any of the three opposition leaders named, but the opposition dismissed the allegations.
Emad Abu Ghazi, secretary-general of the opposition party Mr. ElBaradei heads, said the investigation was "an indication of a tendency toward a police state and the attempt to eliminate political opponents." He said the ousted Mubarak regime dealt with the opposition in the same way. Mubarak jailed his opponents, including liberals and Islamists. International rights groups said their trials did not meet basic standards of fairness.
Mr. ElBaradei was a leading figure promoting the uprising against Mubarak and at one point was allied with the Muslim Brotherhood, of which Mr. Morsi was a leading member, against the old regime.
The investigation does not necessarily mean that charges will be filed against the leaders. But it is unusual for state prosecutors to investigate such broad charges against high-profile figures.
Mr. Morsi, Egypt's first democratically elected president, on Wednesday asked the opposition to join a national dialogue to heal rifts and move on after a month of huge street protests against him and the constitution drafted by his allies. Some protests erupted into deadly violence. On Dec. 5, anti-Morsi demonstrators staging a sit-in outside the presidential palace in Cairo were attacked by Morsi supporters. Fierce clashes ensued that left 10 people dead.
The wave of protests began after Mr. Morsi's Nov. 22 decrees that gave him and the assembly writing the constitution immunity from judicial oversight. That let his Islamist allies on the assembly hurriedly rush through the charter before an expected court ruling dissolving the panel.
After the decrees, the opposition accused Mr. Morsi of amassing too much power. They said the constitution was drafted without participation by the assembly's liberal, minority Christian and women members, who walked out in protest at the last minute.
Even though the constitution passed in a referendum, the opposition has vowed to keep fighting it. They say it enshrines Islamic law in Egypt, undermines rights of minorities and women, and restricts freedoms.
Mr. Morsi and Brotherhood officials accused the opposition of working to undermine the president's legitimacy, and accused former regime officials of working to topple him.
Although he reached out to the opposition for reconciliation, Mr. Morsi did not offer any concessions in his speech calling for a dialogue. The same day, Mr. Morsi asked his prime minister to carry out a limited reshuffle of his government, without offering the opposition any seats.
In an apparent protest against the decision to keep the same prime minister, the minister of parliamentary affairs resigned. This is the second resignation of a Cabinet minister this week and follows a spate of resignations of senior aides and advisers during the constitutional crisis.
Details of the complaint filed by the two lawyers were carried on the website of Mr. Morsi's Muslim Brotherhood, the Islamic fundamentalist group that has become Egypt's most powerful political faction since the 2011 uprising. The report said their complaint alleged that the opposition leaders were "duping simple Egyptians to rise against legitimacy and were inciting against the president," which constitutes treason.
Heba Yassin, a spokeswoman for the Popular Current headed by Mr. Sabahi, said he faced similar charges under Mubarak and his predecessor. She dismissed them as fabrications and a bid to smear his reputation and silence opposition.
"Also, this is evidence of what we had warned about -- the judiciary and the prosecutor-general must be independent and not appointed by the president," she said. "He is a Morsi appointee, and this is where his loyalty lies, and he is now implementing orders to eliminate the opposition."