CAIRO — The leader of Egypt's military declared Sunday that he would not tolerate further violence as his security forces moved to suppress any fresh street protests after bloody days that saw more than 800 people killed, many of them supporters of the Muslim Brotherhood and ousted President Mohamed Morsi.

The Islamist movement that ruled Egypt for a year until it was toppled by the military last month faced a defining moment as hundreds more of its members were arrested, with the interim government freezing its financial assets and vilifying it as a terrorist organization.

"We will not stand by silently watching the destruction of the country and the people or the torching the nation and terrorizing the citizens," Gen. Abdel Fattah Sisi, the head of the armed forces, said in comments quoted on state television.

The military presence throughout Cairo and its suburbs, already at a heightened level in recent days, swelled Sunday, and tanks could be seen throughout most neighborhoods and around squares in the capital. Tahrir Square was closed for a third day.

The Anti-Coup Alliance, a coalition of groups against military rule, posted on Twitter that the protests in one square had been canceled "for security concerns" after the alliance received reports of thugs and snipers on rooftops around the area.

And though the day's major protest march to the Supreme Constitutional Court had not been canceled, a heavy presence of military and police prevented protesters from getting near. As evening approached, the anti-military marchers had yet to reach the court, but dozens of Sisi supporters and members of vigilante groups known as popular committees had descended.

State media reported that 36 members of the Muslim Brotherhood were killed during an attempt to free them as they were transported to prison for 15-day sentences on charges of violence in Ramses Square on Friday and Saturday. Assailants opened fire on security forces in the convoy transporting the detainees, and the forces retaliated with tear gas, according to the Middle East News Agency, with some of those in the truck as well as the attackers killed. However, other media reported conflicting versions of events based on government statements.

The Brotherhood's massive Cairo sit-ins, which had gone on for six weeks before they were broken up Wednesday by security forces, were its most potent political card to challenge Morsi's ouster by the military on July 3. With that gone, the Brotherhood is struggling to regain momentum and keep pressure on an intensifying army presence of tanks and soldiers across the country.

The predicament the Brotherhood faces is reminiscent of the 1950s, when then-President Gamal Abdel Nasser persecuted the group, sending it underground for decades. The Brotherhood remained an outlawed organization through Hosni Mubarak's 30-year rule. When Mubarak's police state was toppled in a 2011 uprising, the organization was transformed from an opposition movement into the nation's most powerful political force.

But it again finds itself as an outcast. It lacks the leadership to guide it through the crisis and its strategy to gain sympathy through protests appears to be waning even though increasing numbers of Egyptians who are not Brotherhood members express anger over last month's coup and ensuing violent crackdowns by the government.

The Brotherhood nonetheless is discovering that millions of Egyptians have endorsed a new wave of nationalism determined to crush any hint of political Islam.

"I don't think the Muslim Brotherhood know precisely what their next steps are, but all the indications say they have decided to continue moving in the streets, in the hopes that maybe international pressure could return to it some of what it lost in Egyptian political life," said Gamal Sultan, a newspaper editor and analyst. "Both parties have decided to continue this confrontation indefinitely."

The repressive tactics by the army and Interior Ministry against the Brotherhood, which still controls an impressive grass-roots network in the provinces, have drawn intense international criticism. Sisi has been portrayed by the U.S. and Europe as setting his nation on a dangerous path.

The Egyptian interim government bristles at what it sees as meddling by foreign powers. It has framed the crisis as a battle between the state and radical Islamists. The government, which is desperate for international investment, has accused foreign media in recent days of distortion.

"Egypt is feeling severe bitterness toward some Western media coverage that is biased to the Muslim Brotherhood and ignores shedding light on violent and terror acts that are perpetrated by this group," according to a statement by Egypt's State Information Service. It added: "Several media sources are seeking to focus on Western political stances that are adopting an approach different from the Egyptian one."

Amid such anger toward the West and the violent crackdown on protests, members of the U.S. Congress remain divided over whether to curtail the $1.5 billion in annual U.S. aid to the Egyptian military, as evident during appearances on Sunday morning news programs.

Sen. Lindsey Graham (R-S.C.), who visited Egypt this month in a failed attempt to broker a political settlement, was among several Republicans who urged the Obama administration to cut off aid. Graham said the crackdown by the Egyptian military risked fueling a domestic insurgency that could threaten Israel's security and wider U.S. interests in the region.

"Somebody needs to look Sisi in the eye and say, 'You're going to destroy Egypt. You're going to doom your country to a beggar state. You're going to create an insurgency for generations to come,'" Graham said on CBS' "Face the Nation."

But Rep. Peter T. King (R-N.Y.) said the United States needs to maintain its relationship with the generals in Cairo to preserve Egypt's peace treaty with Israel, prevent Al Qaeda militants from gaining a safe haven and ensure continued access for U.S. warships and commercial traffic to the Suez Canal.

"There are no good choices in Egypt," King said on "Fox News Sunday," adding, "I think there is more opportunity to protect American interests if we work with the military and continue our relationship with the military."

The split reflects the paucity of good options for Washington in responding to Egypt's spiraling crisis.

The few anti-military protesters who did make it to the constitutional court Sunday also worried about their dwindling options and what the lack of street presence could mean for the opposition.

Walaa Fawzi waited two hours for the marchers to reach the court and finally left as the 7 p.m. curfew neared. "We have been talking about the next steps, but we still don't know what they are," she said.

Ula Kamil, a doctor who helped treat protesters in Rabaa and Ramses, waited beside her. She said she feared what the alternative would be if demonstrations were no longer tolerated.

"We fear if they don't show up, because then they will begin working secretly and committing terrorist acts," said Kamil, who checked her iPhone every few minutes for updates about the marchers' whereabouts. "We are better off for them to come out in the streets and protest."

raja.abdulrahim@latimes.com

jeffrey.fleishman@latimes.com

Special correspondent Ingy Hassieb in Cairo and Times staff writer Shashank Bengali in Washington contributed to this report.