The daughter of American-Israeli released hostage Keith Siegel says her father endured "inhumane conditions" when he was held hostage in the Gaza Strip for more than 15 months.

Siegel's daughter, Shir Siegel, spoke alongside her mother, Aviva Siegel, at the Ichilov Medical Center in Tel Aviv.

“He recounts that he stayed in harsh isolation conditions and at times lost hope that he would ever return home,” said Shir Siegel.

Aviva Siegel, who was held hostage with her husband during her 51 days in captivity, spoke of her "relief" at her husband's release.

She also thanked US President Donald Trump for his role in the release of three Israeli hostages on the weekend, urging Trump to continue his efforts.

"Our hope rests with you to make sure the next stage happens until all the hostages return home," she said.

The family of Israeli hostage, Yarden Bibas, who was released by Hamas-led militants on Saturday, said he was held in very difficult conditions.

Yarden was “kept in harsh conditions of captivity for long periods of time, food was scarce and hygiene conditions were poor, ” his sister, Ofri Bibas-Levy, said from the hospital where he is recovering in Tel Aviv.

She said her brother had lost significant weight and muscle mass due to the difficult conditions, including rarely seeing the sun.

Yarden Bibas was kidnapped separately from his wife, Shiri Bibas, and two children, Ariel and Kfir, who were four years old and nine months when they were kidnapped.