Egypt’s military government is sharply expanding emergency powers to detain people without evidence or official charges, in what critics are decrying as the most significant curbs on personal freedoms here since the fall of Hosni Mubarak.

In the wake of the mob assault on the Israeli Embassy last week, Egypt’s interim leaders are reviving and broadening laws used to detain thousands of dissidents during the Mubarak years, calling the move critical to maintaining law and order in a country confronting a tumultuous transition to democracy. Already, dozens of Egyptians arrested in connection with the embassy attack are being sent for processing in state security courts that are associated with the old emergency laws and that pass sentence without offering defendants the right to an appeal.

The decision finds the interim government walking a tightrope, trying to assure the West and the Egyptian public that it can address an admitted “security vacuum” here while holding on to the faith of pro-democracy and human rights groups. The move comes as the military is being pressed to set dates for parliamentary and presidential elections, against a backdrop of unease among advocates seeking to rapidly usher in a new era of civilian rule.

Groups across Egypt’s political spectrum, including the secular Free Egyptian Party and the conservative Muslim Brotherhood, are vocally denouncing the move as harkening back to the strong-arm tactics many here hoped would be swept away by the Arab Spring.

“The revolution happened to begin with because the emergency law had been active for 30 years in Egypt,” said Bassel Adel, head of the Free Egyptian Party. “It’s not right reactivating this law when the country is in this transitional, non-conclusive phase.”

When Egypt’s military formed a transitional government after Mubarak’s fall in February, political activists here hoped that emergency laws that dated to the 1967 Arab-Israeli war would quickly become a thing of the past. At first, the military authorities gave them reason to believe that might happen, releasing thousands of political and religious prisoners held under such laws, which effectively allowed extended detentions of suspects without trial or even official charges.

But in an announcement Wednesday, the military government signaled that it would not only maintain the laws but also expand them to cover lesser offenses, including interrupting the flow of traffic, interfering with the right to work, engaging in “thuggery” and the spreading of “false information.” Opponents fear the laws could be used by the military to put down a wave of labor strikes, target outspoken politicians or even curb the ongoing protests aimed at pressuring the interim government to move faster in handing over power.

“This is classic military thinking,” said Heba Morayef, Egypt representative for Human Rights Watch. “It’s a reminder that this is the same regime as Mubarak, a regime that does not know what democracy is.”

Those sentiments were echoed in Tahrir Square on Friday, when a crowd of roughly 1,500 activists returned to the symbolic heart of Egypt’s revolution to protest the return and expansion of the emergency laws. “Egypt is supposed to be moving forward,” said Hossam Yehia, a 20-year-old journalism student who took part in the uprisings that ousted Mubarak and was in the square again Friday. “But instead we are moving back.”

Since the uprising, Egypt’s interim government has processed more than 12,000 arrested suspects in military tribunals. By shifting dozens arrested in the Israeli Embassy attack in Cairo to the state security courts, the government has argued that it is at least prosecuting the cases before civilian rather than military tribunals.

An Egyptian government official who defended the move said that the measures were being taken purely for security reasons at a time when the public is fretting about lawlessness and crime and when the attack on the Israeli Embassy threatened to tarnish Egypt’s image abroad.

“The emergency law is being reinforced in order to protect public property and the streets and to stop the people who instigate violence,’’ said the Egyptian official, who insisted on anonymity to speak frankly about the issue. “It will not target views or freedom of expression or criticism,” the official added.

Western diplomats and observers described the move as a serious misstep by a novice military government scrambling to show it is still in charge after unchecked protesters tore down a cement wall at the Israeli Embassy in Cairo last Friday, forcing the emergency evacuation of diplomatic staff. They said Egypt’s military establishment appears committed to holding elections, as promised, but had employed the emergency law as a blunt tool in a bid to reassert authority.

“They had no idea what it was going to be like to run a country,” said a Western diplomat who insisted on anonymity to speak candidly about a sensitive issue. The move, the diplomat said, was being driven by a sense of “panic” to prove the military remains in charge.

Special correspondent Ingy Hassieb contributed to this report.