A Palestinian protester waving a national flag flashes the victory sign as he faces Israeli security forces during clashes with them in the West Bank town of Beita, south of Nablus, on June 3, 2022. AFP
Israeli authorities overnight Sunday-Monday extended the detention of Salah Hamouri, 37, under what is known as administrative detention, according to the documents.
The practise allows suspects to be detained for renewable periods of up to six months.
An Israeli military court sentenced Hamouri to administrative detention in March. It accused him of being a member of the Popular Front for the Liberation of Palestine (PFLP), and said he "endangers security in the region".
Hamouri, who holds French citizenship, denies being a member of the PFLP.
The PFLP has been implicated in several fatal attacks on Israelis and is considered by Israel, the United States and the European Union as a "terrorist group".
The military court documents, sent to his lawyers and seen by AFP, said that his administrative detention has been extended to September 5.
Hamouri has been arrested and jailed by Israeli authorities on several occasions, including in 2005.
Following that arrest, he was tried and convicted by an Israeli court on charges of plotting to assassinate Ovadia Yossef, a prominent Israeli rabbi and spiritual leader of the ultra-Orthodox Shas political party.
Hamouri was released in December 2011 as part of a swap of more than 1,000 Palestinian prisoners for Gilad Shalit, a soldier held captive in Gaza for more than five years.
He has always maintained his innocence.
In April Hamouri, along with rights groups, filed a complaint in France against surveillance firm NSO Group for having "illegally infiltrated" his mobile phone with the spyware Pegasus.
He is one of several Palestinian activists whose phones were hacked using the Pegasus malware, according to a report in November by human rights groups.
Israel says administrative detention is intended to allow authorities to hold suspects while continuing to gather evidence, with the aim of preventing attacks or security offences in the meantime.
But Palestinians, human rights groups and members of the international community have criticised the system. They say Israel abuses the measure.