Human Rights Watch published a report on Tuesday calling on Hamas to confirm that it is holding two Israeli citizens in the Gaza Strip, reveal details on their condition, and release them.

Both Abera Mengistu and Hisham al-Sayeed are believed to have mental problems and to have crossed from Israeli territory into the Strip on their own. Both are being held incommunicado, says the human rights organization.

“Both [Mengistu and al-Sayeed] have histories of wandering far on foot, including across borders without authorization, have not been heard from since they entered Gaza” in 2014 and 2015 respectively, HRW writes.

The report rejects Hamas’ claims that the two are soldiers and goes into their mental conditions in considerable detail. Before they crossed into Gaza, both had a history of protracted absence from their homes.

There are signs that both had been held by Hamas at some stage, says the report. It calls on the movement to unconditionally reveal whether they are in its custody, or any information it has on their whereabouts.

“Hamas’s refusal to confirm its apparent prolonged detention of men with mental health conditions and no connection to the hostilities is cruel and indefensible,” stated Sarah Leah Whitson, Middle East director at Human Rights Watch, adding: “No grievance or objective can justify holding people incommunicado and bartering over their fates.”

HRW contacted Hamas about the two men last September, but the organization said it would not give any answers until Israel releases a number of Hamas prisoners held in Israeli jails.

Hamas also rejected Israeli proposals regarding the release of the two, which would have included transferring the remains of Israeli soldiers Hadar Goldin and Oron Shaul, killed in the Strip during Operation Protective Edge in 2014.

Mengistu, a resident of Ashkelon of Ethiopian descent, was recorded by security camera climbing over a barbed wire fence into Gaza near Zikim Beach beach on September 7, 2014. Al-Sayeed, a Bedouin from the town of Hura in the Negev desert, walked into Gaza in April 2015.

A third Israeli citizen, a young man named Jumaa Abu Ghanima, also crossed from Israel into Gaza in July 2016, but the Israeli defense establishment has not categorized him as a missing person. The HRW report says the Israeli authorities have no information on him being held against his will in Gaza, and the deputy foreign minister of Hamas, Ghazi Hamad, says the organization knows nothing of this third Israeli ostensibly being held by them.

According to Human Rights Watch, Hamas’ position is that "there are no civilians in Israel" and all "Israelis who enter Gaza are spies." HRW takes issue with that contention, stating, “If, as seems the case, Mangistu and al-Sayed entered Gaza in conditions unrelated to the international armed conflict between Israel and Hamas, international human rights law would require authorities to detain them solely according to clear domestic law, which would mean either to charge them with a recognizable crime or release them. The same principles would apply to Abu Ghanima if he is in custody.”

HRW writes that if they are in Hamas custody, they are entitled to “humane treatment that takes into consideration their mental health conditions and any reasonable accommodation required while in detention, as well as access to healthcare services including mental health care.” They should also be visited by the international Red Cross, says the report.

Israeli immigration authorities recently denied a work permit to an HRW researcher on the grounds that the organization serves Palestinian propaganda. Only after the topic was publicized in Haaretz did the Foreign Ministry relent and allow the researcher into the country. He was involved in writing the report on the two missing Israelis.