Hamas leader Mustafa Muhammad Abu Ara was killed in an Israeli prison, bringing the number of detainees killed since Oct. 7 to 19, Palestinian prisoner advocacy organizations reported on Friday.

"The administrative detainee, Sheikh Mustafa Muhammad Abu Ara, 63, from Aqaba in the Tubas province of the northern West Bank, has been martyred," stated the Commission of Detainees’ Affairs and the Palestinian Prisoner Society in a joint release.

The statement added that Ara "died after being transferred from the Israeli Ramon Prison to Soroka Hospital due to a serious deterioration in his health."

Ara, a Hamas leader and former prisoner, had been arrested multiple times since 1990. The latest arrest was from his home on Oct. 30, 2023, it added, noting that before his arrest, Ara suffered from severe health issues and required intensive medical follow-up.

The statement highlighted that "Abu Ara, like all prisoners, faced unprecedented crimes and procedures since the start of the war on Gaza, including torture, starvation and medical neglect, which were primary causes of prisoner deaths in Israeli prisons and camps."

The statement indicated that with the killing of detainee Ara, the number of prisoners and detainees who have been killed since Oct. 7, 2023, has risen to 19.

Israel, flouting a U.N. Security Council resolution demanding an immediate cease-fire, has faced international condemnation amid its continued brutal offensive on Gaza since an Oct. 7 attack by Hamas.

Nearly 39,200 Palestinians have been killed, mostly women and children, and over 90,400 injured, according to local health authorities.

Over nine months into the Israeli onslaught, vast tracts of Gaza lie in ruins amid a crippling blockade of food, clean water, and medicine.

Israel is accused of genocide at the International Court of Justice, which ordered it to immediately halt its military operation in the southern city of Rafah, where more than 1 million Palestinians had sought refuge from the war before it was invaded on May 6.