The IDF on Monday ordered administrative detention for Palestinian Arab journalist and Hamas member Mohammed al-Qiq, AFP reports.
The 34-year-old Qiq was freed by Israel last May from a six-month prison term following a 94-day hunger strike.
He was rearrested last month for his activities in Hamas against Israel, as well as for undermining the Ramallah-based Palestinian Authority.
On Monday, Qiq’s wife Fayha Shalash said he was on hunger strike again. The Israel Prison Service confirmed this, without saying when the fast had begun.
Under Israel's administrative detention law, the state can hold suspects for renewable six-month periods without trial.
The IDF said on Monday Qiq was given the new six-month term based on intelligence that he "continues to be an operative for the Hamas terror group who incites dangerously to harm Israeli citizens".
A military spokeswoman told AFP that administrative detention was "a last resort" measure employed as they had no other way of "neutralizing the danger" Qiq posed.
Qiq denies that he is a member of Hamas and insists he works for the Saudi television channel Al-Majd.
Qiq's case was widely covered last year, and the United Nations expressed concern about his condition during his previous time in prison.
Jailed terrorists have often used hunger strikes as a pressure tactic aimed at forcing Israel to release them out of fear for their lives. Israel has several times in the past caved to the pressure and released some hunger strikers.
Some 1,550 Palestinian Arabs imprisoned in Israel ended a hunger strike in May 2012, in exchange for a package of measures which would allow visits from relatives in Gaza and the transfer of detainees out of solitary confinement.