The Israeli military says an Israeli man was spotted crossing the border fence into the Gaza Strip and is believed to still be inside the Hamas-controlled territory.

The military said it was investigating the circumstances of Tuesday's incident. It said the man was believed to be a member of Israel's Bedouin Arab minority, but gave no other details.

Israel and Hamas are bitter enemies, and Israelis are barred from entering Gaza.

Hamas is believed to be holding two other Israeli civilians who crossed through the heavily-guarded border fence.

Hamas' Interior Ministry declined comment.