A new Israeli air strike killed a man in the central Gaza Strip on Saturday and left a second man clinically dead, Palestinian medical officials said.
They said that the two were hit while riding a motorcycle in the town of Khan Yunis.
Medics said the attack brought to 14 the number of Palestinians killed in 24 hours of cross-border violence in which Israeli aircraft pounded Gaza and Palestinian militants fired at least 70 rockets and mortar rounds into the Jewish state.
It was the deadliest flare-up in more than three years.
The Israeli military said earlier the air force carried out attacks on a range of targets, including a militant leader.
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At least 20 Palestinians were wounded in the string of Israeli air strikes on the Gaza Strip on Friday and Saturday, Palestinian medics said.
The Palestinian barrage on Israel, which started on Friday morning, injured four people, one of them seriously, Israeli military sources said.
Israeli media said that three of the casualties, including the badly wounded man, were agricultural labourers from Thailand working on a farm near the border with Gaza.
One of the retaliatory air strikes killed the head of the Popular Resistance Committees (PRC), Zohair al-Qaisi, and fellow member Mahmud Hanani, the ultra-hardline militant group said.
The PRC threatened reprisals for Qaisi's death.
The Al-Quds Brigades, the military wing of Islamic Jihad, said the air strikes also killed 10 of its members.