Hamas' military wing has claimed it is holding Israeli colonel Asaf Hamami, 41, who the Israeli army previously reported as dead.
The al-Qassam Brigades said Hamami was wounded during his capture, despite Israel previously saying the commander of Gaza’s Division’s Southern Brigade was killed in fighting on 7 October.
The Qassam Brigades did not supply any further evidence and did not specify if the colonel is still alive now.
The group said in a video clip posted on Telegram that the Israeli army leadership is "abandoning its army leaders in captivity" and warned that “time is running out for them”.
Hamami's death was announced by the army's chief rabbi in December, based on apparent findings obtained by the military in Gaza.
The colonel's family went on to hold a funeral according to Jewish law following the announcement.
The Times of Israel reported at the time that thousands of people, including senior military officers and Defence Minister Yoav Gallant, attended the funeral.
"Assaf did not hesitate, he was there, ready to charge the enemy," Gallant said, referring to him as a respected commander and one of the best from the Israeli army in recent years.
An empty casket was carried by friends and mourners at the funeral, as the army said his body remained in Gaza.
Around 250 people were taken captive to Gaza from Israel during the surprise Hamas-led attack on 7 October. The number of captives still alive in Gaza remains unknown.
Israel has waged a brutal war on the Palestinian territory, killing over 35,000 people and wounding over 79,000 others in the same time frame.
The bombardment has levelled entire neighbourhoods in the besieged enclave, plunging it into a deep humanitarian crisis, with UN and aid agencies warning against "catastrophic levels of hunger" and famine in some areas.