Palestinian prisoner rights organisations have accused Israeli prison authorities of “brutally assaulting” Marwan Barghouti, the most prominent Palestinian detainee in Israeli custody.

Prison staff assaulted Barghouti in his solitary confinement cell at Megiddo prison in northern Israel on 9 September, the Palestinian Commission of Detainees’ Affairs, the Palestinian Prisoners’ Club and a support group for Barghouti said in statements.

The rights groups said they were informed of the incident by a lawyer who was able to meet Barghouti on Sunday. It was his first visit in three months, the prisoners’ club told Agence France-Presse (AFP).

The assault “resulted in several injuries to Barghouti’s body, to his ribs … as well as bleeding of the right ear and a wound to his right arm, along with severe back pain”, the groups said.

The Israeli prison service said in a statement to AFP that “Since October 7, Barghouti has petitioned twice, regarding claims of mistreatment in prison. The court has examined every one of his claims and concluded that there has been no violation of the law by IPS.

“Nonetheless, prisoners and detainees have the right to file a complaint that will be fully examined and addressed by official authorities.”

The Palestinian NGOs said Barghouti had endured two assaults since being placed in solitary confinement earlier this year.

A former high-ranking member of the Palestinian Fatah party, Barghouti was arrested in 2002 by Israel and sentenced to life in 2004 for murders. Israel considers him a terrorist and has sentenced him to five life sentences for his role in the second intifada, or uprising, from 2000-05.

Barghouti, now in his 60s, is one of the prisoners whose release could be sought as part of a hostage-prisoner exchange agreement, if a deal is reached between Israel and Hamas.

Palestinian militants are still holding 97 hostages in Gaza, including 34 the Israeli military says are dead.

According to Palestinian prisoner rights organisations, more than 9,000 Palestinians are held in Israeli prisons – more than half of whom were detained after the 7 October Hamas attacks.

An unknown number of Palestinians from Gaza have also been detained by Israeli forces in the territory since the start of the war.

Israel launched its offensive in Gaza after Hamas’s attack that resulted in the deaths of 1,206 people, mostly civilians, according to an AFP tally of official Israeli figures, which includes hostages who died or were killed in captivity.

At least 43,020 people, mostly civilians, have been killed in the Israeli offensive on Gaza, according to figures from the Hamas-ruled territory’s health ministry, which the UN considers reliable.