A Hamas official has demanded 6,000 Palestinian men and women detained in Israel's jails be released in exchange for hostages in Gaza.
The Israeli military said on Monday that 199 captives were being held in the besieged territory - a higher figure than previously estimated.
Khaled Meshaal, head of Hamas' diaspora office, said the hostages include high-ranking officers from the Israeli Defence Forces' Gaza Division, which is responsible for patrolling around the Gaza Strip.
It comes as another Hamas official told Sky News he "does not know" how many hostages are still alive.
Dr Basem Naim, Hamas's head of political and international relations, told Sky News: "I have no idea because it is impossible under this heavy bombardment - the communications are totally cut."
Israel-Gaza latest: Hospital power running out 'within 24 hours'
He also said the ruling Palestinian militant group in Gaza was ready to release civilian hostages when "aggression against our people is stopped".
"At the time the aggression stops, we are ready to release the civilian hostages," he said.
"I hope that we will have hostages alive at the time the aggression ends because al Qassam Brigade [Hamas's armed wing] announced yesterday that nine of the hostages were killed under Israeli bombardment.
"And three days ago 13 others were killed - including four foreigners."
Meanwhile, Sky News has been told that Israel has carried out a strike near the Rafah border crossing from Gaza into Egypt.
Negotiations to open the crossing to allow humanitarian aid into the Gaza Strip - and foreign nationals out - appear to have stalled.
The crossing had been expected to open at 9am local time on Monday.
However, a United Nations spokesperson said there had been no progress on a full opening of the border.
Egypt has accused Israel of not cooperating with the delivery of aid into Gaza via the Rafah crossing, leaving hundreds of tonnes of supplies stuck in the nearby city of Al Arish.
Cairo said on Monday that the border was not officially closed, but instead had been made inoperable due to Israeli airstrikes on the Gaza side.
other key developments:
• Hamas denies Israel's claim it had resumed water supplies to Gaza
• The head of Israel's intelligence agency admits it failed to deter Hamas's attack
• US secretary of state Antony Blinken returns to Israel after six-country tour
• The UN warns fuel at all hospitals across Gaza Strip is running out
• The Israel Defence Forces (IDF) said it killed a Hamas commander in an airstrike
• Rishi Sunak says six Britons were killed in Hamas raid on Israel and 10 others are missing
• He also pledged an extra £10m in aid to help Palestinian civilians
On Monday, a spokesperson for the Israel Defence Forces (IDF) said getting humanitarian aid to the Gaza Strip was "not our responsibility at this time".
Lieutenant Colonel Peter Lerner told Sky News: "Frankly, while the images are extremely concerning, it isn't our responsibility at this time.
"Indeed, we are focused on striking Hamas and striking their capabilities.
"We can't be expected not to defend our civilians because Hamas is hiding behind theirs."
He said the IDF was engaging with humanitarian agencies in the region, but said that the Israeli military was not present in the Gaza Strip to provide aid.
"In the area we have asked them [people in Gaza] to move to and move from - there is no Israeli presence - we cannot provide them with aid," he said.
It comes as Israeli Prime Minister Benjamin Netanyahu attempted to deter Hezbollah from joining the fight, telling the militant group "do not test us" in the north of the country - after 28 towns were evacuated near the border with Lebanon.
The evacuations in northern Israel followed a spike in clashes between the country's military and Hezbollah - a Lebanese militant group backed by Tehran - since Hamas's surprise incursion in Israel on 7 October. Sky News
