Mosab Hassan Yousef — known as the Son of Hamas — called on Israel to kill his father, Hamas co-founder Sheikh Hassan Yousef, if the Palestinian terror organization refuses to release the remaining hostages in the Gaza Strip.

“Israel cannot continue like this … Hamas must have a timeframe – a month or two or six months – to return the hostages and if they don’t return the hostages within the time frame, Israel must execute top Hamas leaders in prison, especially the mass murderers,” Yousef said in a social media post, according to the New York Post.

“When I say execute top leaders, I mean no exceptions, that includes my own father,” he said. “I made a mistake, 10 or 15 years ago when I saved his life many times … He was supposed to die for his actions. I saved his life. Things did not change, things got worse.”

“If this is what Hamas wants, the release of those mass murderers, then in my opinion this is the head of the snake,” he added in a reference to prisons in Israel.

Sheikh Hassan Yousef, a prominent leader of the Hamas Islamic movement, holds the party’s flag and talks on a phone following his release on January 19, 2014. (ABBAS MOMANI/AFP/Getty Images)

Yousef then called on Israel to be even more careful in targeting Hamas to avoid additional civilian casualties.

“I know Israel has avoided targeting civilians, but at this stage, we try even more carefully and we be more precise in our targets,” he said.

With hours left to go before a truce in Gaza expires, international mediators worked to extend it to facilitate the release of militant-held hostages and Palestinians imprisoned by Israel. The ceasefire has paused the deadliest fighting between Israel and Palestinians in decades.

Israel has agreed to extend the truce, which was originally set to expire on Monday, by one day for every ten hostages freed, and Hamas is expected to release another group of hostages later Wednesday. Twelve hostages, including ten Israelis, were released Tuesday, bringing the number of people freed during the truce to 81.

Israel has vowed to resume the war in an effort to end Hamas’s 16-year rule of Gaza, but it is facing mounting international pressure to extend the truce and spare south Gaza a devastating ground offensive like the one that has demolished much of the north.

The Associated Press contributed to this report.