Earlier, Israeli jets struck in Gaza as armed groups there fired rocket barrages toward Israel in response to the death of Khader Adnan, a prominent political leader of the Palestinian Islamic Jihad faction, following an 87-day hunger strike in an Israeli prison.
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 die in Israeli custody in more than 30 years.
Hundreds of people took to the streets in the occupied Palestinian territories to rally and mourn Adnan's 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 salvos fired towards Israel during the day.
The Israeli military said it identified at least 30 rocket launches that set off sirens in southern Israel including in Ashkelon, about 14km north of Gaza, and sent people running to bomb shelters.
Two rockets landed in the small Israeli city of Sderot just east of Gaza, wounding three people, including a 25-year-old foreign national who Israel's ambulance service said sustained serious shrapnel wounds.
Late on Tuesday, plumes of smoke spiralled into the night sky and explosions could be heard as the Israeli military said it hit targets across Gaza including weapons manufacturing sites and training camps of Hamas, the Islamist group that governs Gaza.
Islamic Jihad spokesman Tareq Selmi said fighting had ended by dawn Wednesday.
Two Palestinian officials said Egypt, Qatar and the United Nations helped secure a "reciprocal and simultaneous" ceasefire that largely seemed to hold.
In the West Bank city of Hebron, shops observed a general strike.
Some protesters burned tyres and hurled stones at Israeli soldiers who fired tear gas and rubber bullets at them.
There were no reports of injuries.
Since 2011, Adnan conducted at least three hunger strikes to protest detention without charges by Israel.
The tactic has been used by other Palestinian prisoners 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 has a limited West Bank presence but is the second most powerful armed group in 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 40kg and was having trouble moving and 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 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.
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