On Sunday, Israeli officials pointed to incremental progress in peace talks with Palestinians — appointing joint committees to deal with secondary issues like water, the environment, economic and judicial matters. However, both sides said this was far from a breakthrough, because core issues like Jerusalem, Palestinian refugees and final borders were not involved.

Israel also was taking precautions to keep a Hamas demonstration planned for Monday against its Gaza blockade from turning into a mass breakout like last month's storming of the Gaza-Egypt border.

The Israeli military said its forces operating in southern Gaza Sunday discovered five smuggling tunnels. Soldiers detained 40 Palestinians for questioning.

Barghouti, 44, was a mosque preacher in Kobar and spent several years in Israeli prisons. He was among hundreds of Hamas activists detained by Abbas' security forces in the West Bank following the violent Hamas takeover of Gaza in June. Dozens remain in custody.

Barghouti had an inflamed liver and a serious heart problem when he died, said Justice Minister Ali Khashan. He could not say if Barghouti died because of mistreatment and declined to discuss the case because of the ongoing investigation.

Hamas spokesman Taher Nunu dismissed the investigation, called for by Abbas. "He was tortured to death," Nunu told a news conference in Gaza.

Four men who were arrested alongside Barghouti told his family that they were all tied up in painful positions during interrogation, and that intelligence officers demanded to know where the detainees had hidden weapons.

In a statement published in Palestinian newspapers, the intelligence service said Barghouti had complained of chest and abdominal pain and was examined by a hospital doctor two days before his death. Intelligence officials would not comment Sunday on the allegations.