By Ori Lewis
JERUSALEM (Reuters) - Two Israeli citizens are being held by Hamas in the Gaza Strip, Prime Minister Benjamin Netanyahu said on Thursday, a situation that could lead to demands for a prisoner exchange between Israel and the Islamist militant group.
Hamas, which took control of the Palestinian coastal enclave in 2007 and fought three wars with Israel since then, declined to confirm or deny it had the captives.
"We are working for the return of the two Israelis who crossed the border into Gaza," Netanyahu said in a statement, confirming information that has been restricted by the Israeli military censor since last September.
"We hold Hamas responsible for their safety."
Israel's Defense Ministry identified one of those held as Abraham Mentis, 26, an Israeli of Ethiopian origin. The other is an Israeli Arab who was not named.
The ministry said it believed Mentis, a resident of Ashkelon, a city close to the Gaza border, had crossed into the coastal territory on foot on Sept. 7, 2014. It gave no details on how or when the Israeli Arab had entered the territory.
Mengisto's brother, Ilan, said Avraham was unwell and needed help. In an emotional plea outside the family's apartment in Ashkelon, he called on Hamas to consider his brother's medical state and "release him immediately".
"This is a distressing humanitarian case because my brother is not well," he said. "I ask the Israeli government to bring him home safely and call on the international community to intervene and to bring its influence to bear for his release."
Israel has in the past engaged in prisoner swaps with Hamas, most notably in 2011, when Gilad Shalit, a soldier abducted by militants in a cross-border raid in 2006, was released in exchange for more than 1,000 Palestinians held in Israeli jails.
Dozens of those ex-prisoners have been rounded up by Israel since, outraging Hamas, which signaled that until they were freed again it would refuse to respond to Thursday's charge that it was holding two Israeli captives.
Israel is separately seeking the return of the remains of two soldiers killed during last year's war with Hamas.
"There will be no talk about a prisoner swap before Israel releases all Palestinians who were re-arrested in the West Bank after they had been freed in the 2011 Shalit deal," Mahmoud al-Zahar, a top Hamas official, told Reuters.
Israeli President Reuven Rivlin said the Mengisto family had feared for Avraham's safety before he crossed into Gaza, and that he should not be considered an asset -- a reference to his possible use in a prisoner swap.
"Without discussing (medical) details, his family was very worried about him before he left," Rivlin told reporters. "He cannot be considered to hold tactical or strategic value in the struggle between us and Hamas or any other foes."
Gaza is fenced in by Israel to the north and east and by Egypt to the south. To the west it faces the Mediterranean. In some places the fence between Israel and Gaza is only a few meters high, while it is also possible to swim around into Gaza, although the Israeli military closely monitors such activity.
During the war that ended last August, Hamas fighters infiltrated Israel using cross-border tunnels. Israel says it destroyed these during the fighting, while Hamas says some of the secret passages remained intact or are being rebuilt.
(Additional reporting by Nidal al-Mughrabi; Writing by Ori Lewis; Editing by Luke Baker/Mark Heinrich)