Hamas' armed wing said that six of the captives were killed in two locations in the North governorate, while seven were killed in three locations in the Gaza governorate.
The captives were detained during Hamas’ attack on Israel on Saturday.
Hamas stated on Thursday that “no prisoners’ file will be opened as long the aggression on Gaza continues.”
They also affirmed their “commitment to treating prisoners in accordance with international law.”
Israel had earlier announced that it would not allow aid to flow to the strip until Hamas releases its captives.
"Not a single electricity switch will be flipped on, not a single faucet will be turned on, and not a single fuel truck will enter until the Israeli hostages are returned home," Israeli Energy Minister Israel Katz said on social media.
At least 150 Israelis and foreigners are believed to have been captured been held captives in the Gaza Strip since Hamas' surprise Saturday attack on Israel.
Hamas announced on Monday that Israeli bombardment had killed four captives.
The International Committee of the Red Cross (ICRC) said on Thursday that it is in contact with Hamas and Israel to try to negotiate the release of captives taken into Gaza.
More than 1,200 Israelis were killed and 3,000 others injured since the start of the conflict, according to the Israeli military.
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