Suicide bombers rammed two explosives-packed cars into an Egyptian military intelligence building and an army checkpoint in the volatile Sinai Peninsula on Wednesday, killing 11 people, including six army officers, according to state media reports and a statement from the military.

The bombings in Rafah, near ­the Palestinian-controlled Gaza Strip, are part of a sharp escalation in fighting between Islamist militants and the Egyptian army in the strategically critical desert region that forms Egypt’s border with Gaza and Israel. They also represent yet another problem facing a country that has failed to achieve any viable stability since the ouster of longtime autocrat Hosni Mubarak 31 months ago.

Islamist groups that have operated in the Sinai for years say they are waging war against the Egyptian military regime that took over after the country’s first democratically elected civilian president, Mohamed Morsi, was toppled in July. The militants have launched dozens of attacks on military and police checkpoints in the northern corner of the region, where the sound of gunfire and rocket-propelled grenades is becoming a regular feature of daily life.

The Egyptian military, whose relationship with Israel has strengthened since the coup against Morsi, in turn launched in July what it calls Operation Desert Storm, an offensive that state-run media cast as an effort to finally “cleanse Sinai of terrorist elements and hubs.”

That offensive has intensified since Saturday, with tanks and helicopters sweeping through Rafah and the nearby town of Sheikh Zuweyid, striking at what the military says are Islamist hideouts and weapons depots. Army officials say at least 27 militants have been killed, a death toll that cannot be independently confirmed.

In addition to targeting the Islamists, the military offensive appears to have the larger goal of shutting down the illegal but long-tolerated network of tunnels between Rafah and the Gaza Strip. These tunnels have been a vital lifeline for the coastal enclave, which is under an Israeli-enforced blockade that severely limits the import of building materials and other critical items. Israel says revenue from tunnel-supported trade funds the Islamist movement Hamas, which rules Gaza and is an offshoot of Egypt’s Muslim Brotherhood, which swept Morsi into power.

Egyptian security officials recently leaked plans for the creation of a “buffer zone” along the Egypt-Gaza border, and Rafah residents interviewed by phone said that in the past five days, the military had burned down dozens of homes, torched hundreds of cars and detained or killed many civilians in what they described as an indiscriminate, scorched-earth-style campaign.

“They do not go to any of the houses with real suspects,” said a Rafah resident named Manaa, who did not want to give his last name for fear of being targeted and who said soldiers fatally shot his 65-year-old uncle as he left a mosque. “The army has lost this war because now they have polarized the people of Sinai against them — now they have opened a new front to fight.”

Besides fueling a long-running cycle of violence in the Sinai, the military’s operation may also have prompted a rare attack in Cairo last week, when a suicide car bomber targeted the country’s interior minister, who narrowly escaped unhurt.

The Sinai-based Islamist group Ansar Bayt al-Maqdis claimed to have carried out that bombing and pledged in a statement to continue its attacks in response to the army’s Sinai operation. No group has asserted responsibility for Wednesday’s attacks.

Sharaf al-Hourani contributed to this report.