EL-ARISH, Egypt -- Dozens of Islamic militants unleashed a wave of simultaneous attacks, including suicide car bombings, on Egyptian army checkpoints in the restive northern Sinai Peninsula on Wednesday, killing at least 53 soldiers, officials said.
The advanced planning and coordinated execution of the attacks show that the long-running insurgency in the area is growing stronger, posing a serious threat to Egypt's security as the military-backed government struggles to restore stability after years of unrest since the 2011 uprising.
The assault came a day after Egypt's President Abdel-Fattah el-Sissi pledged to step up the battle against Islamic militants and two days after the chief prosecutor was assassinated in the capital, Cairo. The officials said 50 militants were killed in fierce fighting that started in the early morning and was still raging at the end of the day -- the deadliest battle in Sinai since the 1973 Arab-Israeli war.
Later in the day, a special forces team killed nine members of the outlawed Muslim Brotherhood, including a former member of parliament, in a raid on an apartment in Cairo's Sixth of October district, security officials said. The team was fired upon when they entered the home and returned fire, killing the nine men. No security forces were wounded, said the officials, who spoke on condition of anonymity because they weren't authorized to brief the press.
One of the dead was Nasr al-Hafi, a former deputy in the lower house of parliament for the Brotherhood's Freedom and Justice party, while the other was a Brotherhood leader, Abdel-Fattah Mohamed Ibrahim.
Egyptian officials and pro-government media have blamed a series of recent attacks on ousted President Mohammed Morsi's Muslim Brotherhood, which is officially branded a terrorist group. The Brotherhood has denied involvement in the attacks, many of which have been claimed by other groups, including the Sinai-based militants behind Wednesday's coordinated assault, who are loyal to the Islamic State group.
The Sinai attacks underscored the resilience of the militants, who have battled Egyptian security forces in northern Sinai for more than a decade but have intensified their insurgency since the 2013 military overthrow of Morsi, even as the military has deployed reinforcements, imposed strict curfews and demolished homes and tunnels along the border with Hamas-ruled Gaza.
The Islamic State affiliate claimed Wednesday's attacks, saying its fighters targeted 15 army and police positions and staged three suicide bombings, two that targeted checkpoints and one that hit an officers' club. The claim's authenticity could not be immediately verified but it was posted on a Facebook page associated with the group.
"This specific attack is by far the worst we've ever seen," said Daniel Nisman, CEO for the Levantine Group risk consultancy. "It's not a hit and run -- this is what they used in places like Syria and Iraq to actually capture and hold territory."
He said the attack revealed the weaknesses of the military's "scorched earth" operations against militants in the northern Sinai, which he says have made it difficult for an army that is "very, very overstretched" to recruit local support.
The assault focused on the town of Sheikh Zuweid and targeted at least six military checkpoints, the officials said. The militants also took soldiers captive and seized weapons and several armored vehicles, they added, speaking on condition of anonymity in line with regulations.
The officials said scores of militants were besieging Sheikh Zuweid's main police station, shelling it with mortars and rocket-propelled grenades and exchanging fire with dozens of policemen inside.
At least 55 soldiers were wounded, the officials said. As fighting raged, an army Apache gunship destroyed one of the armored carriers captured by the militants as they were driving away, the officials said.
An Associated Press reporter meanwhile heard two explosions from the Egyptian side of the Rafah border crossing with Gaza and saw smoke rising, though it was not immediately clear what caused the blasts or if they were linked to the militant assault some 40 kilometers (25 miles) away.
Egypt's military spokesman, Brig. Gen. Mohammed Samir, said clashes were still underway in and around Sheikh Zuweid and that 10 soldiers had been killed. The conflicting accounts of the number of troops killed could not immediately be reconciled.
Samir's statement, posted on his official Facebook page, said some 70 militants attacked five checkpoints in northern Sinai and that Egyptian troops killed 22 of them and destroyed three all-terrain vehicles fitted with anti-aircraft guns.
Later Wednesday, Samir said on his Facebook page that the country's armed forces targeted two militant gatherings in northern Sinai, completely destroying them.
The Egyptian air force is "targeting terrorists on the ground as clashes continue," he said, though he did not give a new figure for militant casualties.
Two of the six checkpoints attacked Wednesday were completely destroyed, the officials said. Army checkpoints in the area are routinely staffed by 50-60 soldiers. The IS statement said the two checkpoints were hit by suicide bombers.
Last week, Islamic State spokesman Abu Mohammed al-Adnani issued an audio statement calling for massive attacks during the Muslim holy month of Ramadan, now entering its third week.
Militants in northern Sinai, which borders Israel and the Gaza Strip, stepped up their attacks following the July 2013 military ouster of Morsi after days of mass street protests against his rule. Last year the main insurgent organization operating in Sinai pledged allegiance to the IS group, calling itself Sinai Province.
The territory, characterized by hardscrabble towns, desert and mountainous areas suitable for guerrilla operations, has long been neglected by the state. Local Bedouin tribesmen have grown to resent Cairo, turning to smuggling, organized crime and, in some cases, radical Islam.
El-Sissi, who as army chief led Morsi's overthrow, was elected president last year on a ticket that emphasized security and economic recovery.
Wednesday's attacks came in swift response to his pledge the previous day to bring to justice those behind the assassination of Egypt's prosecutor general the day before.
Pounding his fist as he spoke Tuesday at the funeral of Hisham Barakat, who oversaw scores of cases against thousands of Islamists, el-Sissi signaled an even tougher campaign against Morsi's Muslim Brotherhood and the possible execution of Morsi and other Brotherhood leaders who have received death sentences in recent months.
Since Morsi's ouster, Egypt has arrested thousands of Islamists and other dissidents, convicting hundreds in collective trials and issuing mass death sentences. Morsi is among those condemned to die, but has a potentially lengthy appeals process ahead of him.
Though el-Sissi's crackdown on Islamists has been criticized by rights groups, activists, and some Egyptians, most of the population supports his battle against Islamic radicals in Sinai.
"The judiciary is restricted by laws, and swift justice is also restricted by laws. We will not wait for that," el-Sissi said on Tuesday.
Action will be taken within days "to enable us to execute the law, and bring justice as soon as possible," he added. "We will stand in the face of the whole world, and fight the whole world."
In a thinly veiled reference to jailed members of the Brotherhood, el-Sissi blamed the violence on those "issuing orders from behind bars," and warned: "If there is a death sentence, it will be carried out."
Associated Press writers Hamza Hendawi in Beirut, Merrit Kennedy in Cairo, and Ian Deitch in Jerusalem contributed to this report.