Relatives mourn victims of the Palm Sunday bombings during a funeral at the Monastery of Saint Mina in Alexandria, Egypt, on April 10, 2017. (Amr Abdallah Dalsh/Reuters)

A day after deadly Islamic State bombings struck two Egyptian churches, Israel closed its southern border with Egypt’s Sinai Peninsula on Monday and urged Israelis to leave Egypt amid worries of another round of militant attacks.

Shortly after the announcement, Israel’s military said that a rocket fired from Sinai exploded in southern Israel. No injuries or damage were reported.

But the incident — and border closure — underscored the growing strength of Egypt’s Islamic State affiliate, which is based in Sinai. It also reflected the security challenges facing the government of Abdel Fatah al-Sissi, who has vowed to eradicate Islamist extremists from the country and protect Egyptians of all faiths.

In its statement, the Israeli government said its intelligence indicated “increased activity” by the Islamic State in the Sinai Peninsula and a “desire to commit terrorist attacks against tourists in Sinai, including Israelis, in the immediate term.”

“The [Egyptian] military is incapable of controlling the Sinai,” said Mohannad Sabry, an Egyptian journalist and author of a book on the Islamist insurgency in Sinai.

The border closure appeared triggered by the bombing of Coptic churches on Sunday in the northern Egyptian cities of Tanta and Alexandria that killed at least 44 people and injured more than 100. The attacks, carried out by suicide bombers and claimed by the Islamic State, came as worshipers gathered for Palm Sunday services.

Sissi declared a three-month state of emergency, three weeks ahead of Pope Francis’s scheduled visit to Egypt.

Israel’s intelligence minister, ­Israel Katz, said the Islamic State’s activities in Sinai have intensified in recent months “due to pressures in Syria and Iraq, which has increased the group’s motivation to carry out attacks in other arenas.”

The well-armed affiliate — known as Wilayat Sinai — has grown bolder since it asserted responsibility for the October 2015 bombing of a Russian charter flight over the Sinai Peninsula, killing all 224 aboard. Since then, the group has waged a steady military campaign against Egyptian soldiers, overrunning military posts and targeting them with roadside bombs.

But in December, the Islamic State changed tactics and orchestrated a bombing at Cairo’s Coptic Christian cathedral complex that killed at least 25 people and wounded 49. Since then, Christians have become a primary target in its campaign against the government.

Hundreds of Christians fled the Sinai Peninsula this year after the militants began killing members of their community. In a February video, the extremists warned that they would escalate attacks against Christians.

Sunday’s church bombings were hundreds of miles from the militants’ main base of operations, suggesting that they are able to mobilize fighters, weapons and explosives in urban areas, analysts said.

“It is a message that ISIS is sending to say that they have the upper hands in Egypt,” said Yousri el Ezabawy, an analyst of religious and extremist groups at Al-Ahram Center for Political and Strategic Studies. “This will boost their capabilities to attract more members and bring them to Egypt, from Syria and Iraq. It would also assure those who fund them that they are successful in Egypt, and hence get more funding and power.”

On Monday, dozens of funerals were held in both cities for the victims.

Hundreds of black-clad mourners joined in processions of wooden coffins and beating drums. Many said the government had failed to protect its Christian minority, which accounts for about 10 percent of the population of about 95 million.

By increasingly targeting Christians, the Islamic State sees propaganda value, analysts said. Every attack receives worldwide attention and bolsters the image of the Islamic State’s Sinai affiliate within Islamist militant circles. It also embarrasses the Sissi government.

“It immediately shows the state is not in control, that it’s incapable of protecting Christians,” Sabry said.

After the bombings, Israel’s ­anti-terrorism office urged Israeli tourists in southern Sinai to return home immediately through the Taba border crossing, which remains open for Israelis.

The office also asked Israelis to cancel planned trips to Sinai, where they have long flocked to the picturesque beaches and azure waters of the Red Sea, especially during the Passover holiday.

Passover, which began Monday evening, commemorates the biblical story of the Israelites’ flight from slavery in Egypt. As in most years, about 20,000 Israeli tourists were expected to pass through the Taba crossing into Sinai.

Zack Gold, a nonresident fellow at the Atlantic Council’s Hariri Center in Washington, said that Israel’s decision to close its border crossing into Egypt’s Sinai Peninsula was an unusual step.

The Islamic State in Sinai, he said, had changed tactics recently, targeting civilians and carrying out stated threats.

“For years, they’ve said, ‘We’re going to target Israel,’ but have not put their resources to that,” he said. “Now, they’re saying, ‘We’re going to target Christians,’ and they are targeting Christians, so Israel has to decide if it’s time to take the rhetoric seriously.”

Eglash reported from Jerusalem. Heba Mahfouz in Cairo contributed to this report.