Palestinian armed groups fired salvoes of rockets from Gaza into southern Israel on Tuesday after an Islamic Jihad leader died in Israeli custody following an 87-day hunger strike, the first such death in more than three decades.

Khader Adnan, who was awaiting trial, was found unconscious in his cell and taken to a hospital, where he was declared dead after efforts to revive him, Israel’s Prisons Service said.

Hundreds of people took to the streets in blockaded Gaza and the occupied West Bank to rally in support of Adnan and mourn his death, which Palestinian leaders described as an assassination. In Gaza, an umbrella group of armed Palestinian factions, including Hamas and Islamic Jihad, launched two separate rocket barrages towards Israel.

The Israeli military said at least three rockets were fired from Gaza in the hours after Adnan’s death and a further 26 were launched later in the afternoon. Two landed in the southern city of Sderot, wounding three people, including a 25 year-old foreign national who Israel’s ambulance service said sustained serious shrapnel wounds.

An Israeli Defence Force official said Israel would respond at a time and a place of its choosing.

Prime Minister Bejnamin Netanyahu held a meeting with security officials to assess the situation and the military said it was investigating how two rockets had penetrated the Iron Dome air defence system.

Since 2011, Adnan had conducted at least three hunger strikes in protest at detentions without charges by Israel. The tactic has been used by other Palestinian prisoners, sometimes en masse, but none had died since 1992.

Adnan’s lawyer Jamil Al-Khatib and a doctor with a human rights group who recently met him accused Israeli authorities of withholding medical care.

“We demanded he be moved into a civilian hospital where he could be properly monitored. Unfortunately, such a demand was met by intransigence and rejection,” Al-Khatib told Reuters.

Adnan, 45, was a baker and a father of nine from Jenin in the Israeli-occupied West Bank. Islamic Jihad sources said he was one of its political leaders. The faction has a limited West Bank presence but is the second most powerful armed group in Hamas-ruled Gaza, where Israeli forces fought a brief war against it last August.

Lina Qasem-Hassan of Physicians for Human Rights in Israel said she saw Adnan on April 23, at which point he had lost 40 kg (88 pounds) and was having trouble breathing but was conscious.

“His death could have been avoided,” Qasem Hassan told Reuters, saying several Israeli hospitals had refused to admit Adnan after he made brief visits to their emergency rooms.

The Prisons Service said hospitalisation had not been an option as Adnan had declined “even a preliminary inspection”.

‘Fight is continuing’

Physicians for Human Rights said Israeli authorities had denied requests by Adnan and his family to visit him in prison.

Speaking from the family’s home in the northern West Bank town of Arraba near Jenin, Adnan’s wife, Randa Musa, said: “Our message to all the resistance groups is, we do not want the weapons that were not used to free the sheikh (Adnan) to be used after his death. We do not want to see any bloodshed.”

Adnan’s 9 year-old son Ali led a march through Arraba. Perched on a man’s shoulders, he chanted, “Khader, you hero, your name shook the prison!” as dozens followed.

Tuesday’s rocket barrages came almost a month after the last cross-border exchanges of fire between Israel and Gaza, which followed an Israeli police raid in the al-Aqsa mosque complex during the Muslim holy month of Ramadan.

“Our fight is continuing and the enemy will realise once again that its crimes will not pass without a response,” Islamic Jihad, which preaches Israel’s destruction, said in a statement.

Israel said it was cancelling a military drill that had been planned for the areas surrounding Gaza “pursuant to a situational assessment”, and was putting staff in security prisons on heightened alert.

According to the Palestinian Prisoners Association, Adnan had been arrested by Israel 12 times, spending around eight years in prison, mostly under so-called “administrative detention” - or detention without charges.

Israel says such detentions are required when evidence cannot be revealed in court due to the need to keep intelligence sources secret. Palestinians and rights groups say they deny due process of law.

This time, Adnan was arrested and indicted in an Israeli military court on charges that included links to an outlawed group and incitement to violence, the Prisons Service said.