A shadowy jihadist group based in Egypt’s restive Sinai Peninsula claimed responsibility Monday for a weekend car bombing in a major Suez Canal city, underscoring the growing threat posed by Islamist extremists in Egypt nearly four months after a coup.

Ansar Bayt al-Maqdis, also known as Ansar Jerusalem, said in a message posted on jihadist forums that it was behind the explosion, according to the SITE monitoring group, which tracks extremist Web sites.

The attack in Ismailia, which wounded 11 people, including six soldiers, was the third bombing carried out by the group in less than two months, and it highlighted the militants’ ability to strike government targets outside the Sinai Peninsula, despite intense efforts by the military to fence them in.

Ansar Bayt al-Maqdis, which analysts say is made up mostly of local Bedouins, as well as some foreign fighters, established its presence in July 2012 when it asserted responsibility for a series of bombings targeting a pipeline carrying gas from Egypt to Israel. Until recently, it had focused its attacks on Israel, analysts said.

Since the July 3 coup that ousted Islamist President Mohamed Morsi, militants have launched near-daily attacks on military and police targets in North Sinai, an area known for lawlessness and smuggling along Egypt’s border with Israel and the Gaza Strip.

But the attack in Ismailia was especially significant. Like an attack in September on Egypt’s interior minister, it showed that the group had breached the Suez Canal, which serves as the physical boundary between mainland Egypt and the Sinai. Ismailia is home to many Morsi supporters.

The military has responded to the violence in Sinai by tightening security at the bridge and tunnel connecting the region to the rest of Egypt, demolishing smuggling tunnels along the Gaza border, and razing homes of suspected militants.

Ansar Bayt al-Maqdis said Saturday’s attack outside a military headquarters in Ismailia was in reprisal for “the repressive practices carried out by the Egyptian army against our people in Egypt, such as killing the citizens, demolishing homes, and arresting at random without guilt or fault,” according to a statement translated by SITE.

Sinai’s majority-Bedouin population long complained of discrimination and abuse under authoritarian President Hosni Mubarak. After he was forced from power in 2011, Bedouin tribal communities chased security forces from their posts, creating a vacuum in which jihadist cells have flourished.

Political analysts say Egypt’s powerful military and security forces, which have killed and imprisoned thousands of Morsi’s supporters since the coup, are poorly equipped to tackle a grass-roots insurgency. “The Egyptian army has always been trained in the heavy weaponry that is only used in conventional wars,” said Mohamed Kadry Said, a retired major general and an analyst at the state-run al-Ahram Center for Political and Strategic Studies.

The government battled an Islamist insurgency in southern Egypt in the 1990s. Mubarak’s security forces detained thousands of people, some for years, and rarely with due process. “Our intelligence services knew how to handle it back then,” Said said.

Ansar Bayt al-Maqdis is a “homegrown” North Sinai organization, said Aviv Oreg, a security consultant and former head of the global jihad desk in Israel’s military intelligence. The group’s members may communicate with al-Qaeda through the Internet and employ al-Qaeda-style tactics such as suicide bombers, but “they don’t have external leadership from Al-Qaeda,” Oreg said. “They execute attacks in their own time based on their own capabilities.”

In addition to the attacks on a pipeline that carries Egyptian natural gas to Jordan and Israel, Ansar Bayt al-Maqdis was behind a 2012 cross-border raid that left 16 Egyptian soldiers dead and ended in a confrontation with Israeli forces.

In August, the group said four of its fighters were killed in an Israeli drone strike as they prepared to fire rockets over the border from North Sinai.

Oreg said that “tactically and strategically” the group also appears to have coordinated attacks with Palestinian groups inside Hamas-run Gaza.

The group’s most recent attacks have focused on the Egyptian government. On Oct. 7, Ansar Bayt al-Maqdis sent an explosives-laden car crashing into the gate of a security headquarters in South Sinai, setting off an explosion that killed three police officers. A month earlier, the group asserted responsibility for an assassination attempt on Egypt’s interior minister in Cairo. He survived, but the bombing killed a police officer and wounded more than 20 people.

“We direct an apology to the Muslim masses in general and the relatives of the martyrs in particular for not killing this criminal tyrant this time,” the group said in a communique published on jihadist forums on Sept. 8, three days after the attack, according to SITE. “And we promise them that the attacks of the mujahideen will be repeated upon him and upon those like him,” it added.

William Booth in Jerusalem contributed to this report.