CAIRO — Foes of Egypt’s military-appointed government carried out three brazen attacks on Monday, killing six soldiers in a drive-by shooting near the Suez Canal, bombing a security building in the tourist-dependent southern Sinai that left at least three police officers dead, and firing grenades at a Cairo compound housing the country’s main satellite transmitter.
There were no immediate claims of responsibility for the attacks, and no indication that they were coordinated in any way. But they came a day after the worst street clashes to convulse Egypt since mid-August, raising new questions about the interim government’s success in stabilizing the country. At least 51 people were killed in the street clashes, and hundreds were injured, as the Muslim Brotherhood constituency of the ousted president, Mohamed Morsi, continued to mount protests and be met with a violent crackdown by the military.
Ahram Online, the Web site of the Egypt’s main newspaper, said the six soldiers who were killed Monday near the canal were on patrol in a pickup truck outside the city of Ismailia when they were attacked by masked gunmen in another vehicle. Everyone in the trick was killed, the newspaper said.
The bombing of the security building took place in the town of el-Tor in the southern Sinai, the region where Egypt’s famed Sharm el-Sheik resort is located. The location of the attack was a departure; most of the near-daily attacks by radical Islamists in Sinai have been against security forces in the north.
The attack on the satellite transmitter in the Maadi district caused no casualties and only minor damage, but it appeared to represent a new level of audacity by opponents of the interim government. Sky News Arabia, a pan-Arab news channel, said that armed assailants attacked the facility with rocket-propelled grenades.
The military-backed government that replaced Mr. Morsi has tried to project an aura of stability in Egypt, hoping to lure back the tourists and investors who were scared off by several years of turmoil in the country.
But on Sunday, only grim, familiar scenes of violence returned, along with the sounds of gunfire.
The street clashes came as thousands of Egyptians celebrated the 40th anniversary of the 1973 war with Israel, setting up a day of bizarre contrasts that served as reminders of Egypt’s deepening polarization.
As the military’s supporters celebrated the anniversary in Tahrir Square in Cairo with music and fireworks, officers and armed civilian loyalists set upon Islamist protesters who were also trying to reach the square, driving back their marches with tear gas and gunfire.
More than 250 people were injured, officials said.
Over the last three months, with little resistance from the public, the military has set out to vanquish the Muslim Brotherhood, the Islamist group that propelled Mr. Morsi to power. Since July, hundreds of Brotherhood members have been killed and most of the movement’s leaders have been sent to jail or fled the country.
And Mr. Morsi’s Islamist supporters, who have re-branded themselves under the banner of the “anti-coup” movement, have continued to protest despite the repression of their marches and sit-ins, and dwindling attendance at their demonstrations.
They had billed the protests on Sunday as their own tribute to the armed services, while promising a new level of confrontation: for the first time since Mr. Morsi’s ouster, they called for marches on Tahrir Square, a stronghold of the anti-Morsi movement.
The decision to call for demonstrations on Oct. 6, the anniversary of the 1973 war, also seemed part of a persistent, but so far fruitless, effort by the Islamists to identify cracks in the military, Egypt’s most powerful institution.
In a statement last week, the anti-coup protesters said they intended to salute “the soldiers who fought the October war — so our brave army regains its commitment to the true Egyptian military doctrine and knows the difference between the enemy and its people, before it turns into militias that do not have any other mission but killing its own people.”
The military-backed government responded by calling for its own commemoration of the war in Tahrir Square, setting up the likelihood of a bloody confrontation between civilians. On Saturday, a spokesman for the interim president said that protesters against the military were “agents, not activists.”