An explosion is seen as Israel strikes Gaza. [Source: Reuters]

Israeli jets hit targets across the Gaza Strip, in response to rocket barrages fired by militant groups earlier in the day following the death of a Palestinian hunger striker in Israeli custody.

Plumes of smoke spiralled into the night sky as the jets hit targets including training camps of Hamas, the Islamist group that controls the coastal enclave.

At the same time, sirens sounded near the southern Israeli town of Sderot and other areas around Gaza as Hamas radio reported that militant factions were continuing their bombardment of Israeli targets.

The fighting, around a month after the last cross-border exchange of fire between Israel and Gaza, came after the death of Khader Adnan, a senior member of the Islamic Jihad group, who died after 87 days on hunger strike.

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. He was the first Palestinian hunger striker to have died in an Israeli prison in more than 30 years.

Hundreds of people took to the streets in blockaded Gaza and the occupied West Bank to rally in support of Adnan and to mourn his death, which Palestinian leaders described as an assassination.

In Gaza, an umbrella group of armed Palestinian factions, including Hamas and Islamic Jihad, claimed responsibility for a series of rocket barrages fired towards Israel during the day.

The Israeli military said at least 26 rockets were fired from Gaza. Two landed in Sderot, wounding three people, including a 25-year-old foreign national who Israel’s ambulance service said sustained serious shrapnel wounds.

In the West Bank city of Hebron, shops observed a general strike. Some protesters burnt tires and hurled stones at Israeli soldiers who fired tear gas and rubber bullets at them. There were no reports of injuries.

Prime Minister Benjamin Netanyahu met security officials to assess the situation. An Israeli Defence Force official said Israel would respond at a time and a place of its choosing.

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.

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 moving and breathing but was conscious.

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

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.”

Before the rockets, Hamas radio said an Israeli tank shelled one of the group’s observation posts in Gaza.

Member of Hamas’s political wing Zakaria Abu Maamar said further rocket fire from Gaza will be aimed at “all parts of the homeland”.

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 Israel routinely uses such detentions, which deny due process, to hold hundreds of Palestinians for prolonged periods of time.

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.