The army said it hit Gaza with "tank fire" in response to rockets from the Palestinian enclave, sparking a renewed volley from Gaza that was witnessed by AFP journalists.

The exchange of fire came hours after 45-year-old prisoner Khader Adnan died, nearly three months after being detained in the occupied West Bank over his ties to the Islamic Jihad militant group.

Palestinian prime minister Mohammad Shtayyeh described his death as a "deliberate assassination", charging Israel had killed him "by rejecting his request for his release, neglecting him medically and keeping him in his cell, despite the seriousness of his health condition".

News of his death was initially followed by three rockets fired by militants from Gaza, the Israeli army said.

Israel's retaliatory tank fire was met with a further 22 projectiles launched from Gaza, the military reported.

A joint statement by militant factions in Gaza, including the territory's rulers Hamas and Islamic Jihad, said the rocket fire was an "initial response" to Adnan's death.

The Magen David Adom emergency service said three people were wounded with shrapnel in the Sderot area, near the Gaza border.

After meeting with the military chief, Defence Minister Yoav Gallant warned "anyone who attempts to harm the citizens of Israel will be sorry."

- 'Deliberate medical negligence' -

Israel's prison service had announced the death of a detainee who was affiliated to Islamic Jihad, saying he was "found early this morning in his cell unconscious".

Adnan was the first Palestinian to die as a direct result of a hunger strike, according to advocacy group the Palestinian Prisoners' Club.

Other Palestinian detainees have died "as a result of attempts to force feed them", said the group's director Qaddura Faris.

Palestinians launched a general strike in West Bank cities in response to Adnan's death.

Israel's far-right National Security Minister Itamar Ben-Gvir said prison officials decided to close cells to "prevent riots".

"The directive to the prisoner service is zero tolerance towards hunger strikes and disturbances in security prisons," he said.

- 'Pay the price' -

A senior Israeli official described Adnan as "a hunger striker who refused medical attention, risking his life".

"The military appeal court decided against releasing him from detention solely on the merit of his medical condition," said the official, who requested anonymity because they were not authorised to speak publicly to the media.

Adnan was described by the official as an "operative" of Islamic Jihad, who was facing charges related to his activities within the militant group.

Israel has occupied the West Bank since the 1967 Six-Day War and its forces regularly detain Palestinians, who are subject to Israeli military courts.

Islamic Jihad, which is considered a terrorist organisation by the European Union and the United States, warned Israel would "pay the price for this crime".

Israel's prison service said Adnan was in jail for the 10th time and his wife, Randa Mousa, previously told AFP her husband had carried out multiple hunger strikes in detention.

- Family against Gaza rockets -

Speaking on Tuesday, Mousa said she was proud of her husband's "martyrdom" which the family wears like "a crown on our heads".

But she cautioned militants against launching a violent response.

"We don't want a drop of blood to be shed," she told journalists in the family's hometown of Arraba in the northern West Bank.

"We don't want anyone to respond to the martyrdom. We don't want someone to launch rockets and then (Israel) strikes Gaza."

In his final message, Adnan said he was "sending you these words as my flesh and fat has melted".

"I pray that God accepts me as a faithful martyr," he wrote, in a message published Monday by the Palestinian Prisoners' Club.

Physicians for Human Rights Israel said its medic visited Adnan and raised his "life-threatening condition and the need for immediate hospital transfer".

Israeli rights group BTselem described his hunger strike as "a form of non-violent protest against his arrest and the injustices of the occupation".

"The fact that a person whose life was in danger remained in prison despite repeated requests to transfer him to a hospital reflects the absolute disregard Israel held for his life," the organisation said.