Avraham Mengistu, an Israeli citizen of Ethiopian origin, is allegedly being held by the Hamas militant group. (Family Handout/EPA)

Usually people are desperate to leave Gaza. But an Israeli named Avraham Mengistu decided to slip across the border fence, bristling with high-tech sensors and protected by remote-controlled machine guns, and enter the Gaza Strip.

That was 10 months ago. His fate is unknown, though Israel says he is probably being held by armed Palestinian factions.

News of the Ethiopian Israeli’s puzzling disappearance had been suppressed in the Israeli media until now under a military gag order. Israel and the Islamist militant group Hamas, which controls Gaza, fought a 50-day war last year that ended in August. Mengistu, 28, entered the coastal enclave the following month.

Israeli soldiers found a suitcase he had left behind on the beach near the fence. It contained a Hebrew Bible

Family members charged that Mengistu’s disappearance and possible capture by Hamas would have been treated far differently if he were not of African descent. In recent months, Ethiopians have staged large demonstrations to protest what they call racist treatment by Israeli police and society.

Israeli media reported on the case for the first time on Thursday, revealing that Israeli officials, through intermediaries, have been seeking information about Mengistu’s whereabouts for months.

The Israeli military agency that oversees access to Gaza said in a statement that “according to credible intelligence,” Mengistu is being held “against his will” by Hamas.

Hamas officials have declined to comment on the case.

“Israel has appealed to international and regional interlocutors to demand his immediate release and verify his well-being,” the Israeli government said in a statement.

Israeli President Reuven Rivlin said Thursday: “This is a humanitarian matter, and I expect those holding him to treat him properly and to return him in full health.”

Israeli officials also revealed that a second Israeli citizen, an Arab, was being held in Gaza. The government declined to provide details.

In a statement Thursday, Israeli Prime Minister Benjamin Netanyahu said: “We are working to return the two Israelis who crossed the fence into Gaza. We hold Hamas responsible for their welfare.”

He added: “Yesterday I spoke with the parents and siblings of Avraham Mengistu and I told them that from as soon as the incident became known we have spared no effort to return him to Israel. We agreed to meet soon.”

In a jab at foreign critics of Israel’s actions in the Palestinian territory, Netanyahu concluded pointedly, “I expect the international community, which expresses its concern over the humanitarian situation in Gaza, to issue a clear call for these citizens to be released and to see to their return.”

The case of Mengistu, whose name also has been rendered as Avera Mangisto, is unique and bizarre.

Most Israelis live in mortal terror of entering the Gaza Strip. Israelis — even dual nationals and journalists — are forbidden to enter the enclave, partly out of fear that they will be kidnapped by armed Palestinian factions and used as bargaining chips for the release of Palestinian prisoners held by Israel.

Mengistu’s brother Yalo, 32, told the Israeli newspaper Haaretz that the family was not briefed by Israeli military officials until two weeks after his sibling crossed the fence. “We’re sick of it. We want to go public with the story,” he said.

Yalo Mengistu told the newspaper that his family’s initial attempts to meet with Netanyahu were rebuffed.

Another brother, Ilan Mengistu, refrained from criticizing the government at a brief news conference at the family’s apartment in southern Israel on Thursday. The family “has decided to behave with restraint and give the government time to get our brother back home, and we also ask the people of Israel to show restraint,” he said.

He added that Avraham Mengistu was not healthy, and he pleaded with the international community for help and for Hamas to release him.