An Israeli security official says the Hamas militant group has been holding an Israeli citizen in the Gaza Strip for nearly a year.

The official says the Israeli of Ethiopian origin ran past the border fence into the Gaza Strip last September shortly after the end of the Israel-Gaza war and has been held by Hamas since.

The official says it is unclear why he entered Gaza, and that he is believed to be mentally unstable. The official says Israel does not consider the Israeli to be a captive, and that Israel was treating the matter as a humanitarian issue.

The official spoke on condition of anonymity because he was not authorized to speak publicly about the matter.

Hamas declined comment.

Israeli media released details of the matter Thursday.