Three air strikes on Monday night in the Gaza Strip killed nine members of the group, while an Israeli military operation in the West Bank left another dead.
Later on Tuesday morning, an Israeli air raid in the southern Gaza town of Khan Younis killed one of Hamas's security-force members.
The raids came just hours after a conference in Paris attended by 90 countries pledged $7.4bn in aid over three years to the Palestinian Authority.
The first raid in Gaza City, late on Monday, killed Majed al-Harazin, commander of al-Quds Brigades for Gaza and the West Bank, a man wanted by Israel for the past nine years.
By the time the raids were over, also dead was Karim al-Dahdouh, a master rocket-maker.
An Israeli military spokeswoman said al-Harazin was targeted for "supervising commandos responsible for firing rockets at southern Israel".
Palestinian officials said he was the most senior commander to be killed in an Israeli raid in Gaza in more than a year.
His car was reported to be full of explosives and a huge explosion could be heard across the city.
A second man was also killed in this attack.
Series of attack
Hundreds of Islamic Jihad fighters gathered in the streets and fired into the air after al-Harazin's killing on Monday.
Hours later, a second Israeli attack killed four more Islamic Jihad fighters, including a rocket maker, on the streets of Gaza City, the group said.
Three of the men died immediately, with a fourth man succumbing to his wounds in hospital hours later.
The Israeli military spokeswoman said the attacks targeted fighters preparing to fire rockets at Israel.
Palestinian medical workers said the attacks wounded two bystanders.
A third air raid, also confirmed by the Israeli military, killed three Islamic Jihad fighters in a car near the northern town of Beit Lahiya, as they emerged from morning prayers, medics said.
Meanwhile, in the occupied West Bank, 25-year-old Tarek Abu Rali, a local commander of the al-Quds Brigades, was killed by undercover Israeli soldiers as he drove in a car in the northern town of Jenin, medics and Islamic Jihad said.
Blow to peace
Mukhaimar Abu Sada, a political analyst from Gaza, told Al Jazeera that the Israeli attacks diminished hopes for a successful peace process.
But Matan Vilnai, Israel's deputy defence minister, hailed the "successes", saying the military was targeting the leadership of the group.
|In overnight Gaza raids, Israel killed nine|
fighters belonging to Islamic Jihad [AFP]
Speaking to the military's radio station, he said: "The important thing is not the number of them who are hit, but their place in the organisation's hierarchy."
Meeting members of his Kadima party in Jerusalem late on Tuesday, Ehud Olmert, the Israeli prime minister, pledged to keep up the pressure.
"We will continue to seek out the heads of the terror organisations," he said.
"We will get all those who are responsible for firing rockets. The terror organisations feel this and will feel this in full force in the near future."
Calls have grown in Israel over the past several months for the military to launch a widespread ground offensive in Gaza to put an end to the daily firing of rockets and mortars from the Hamas-run territory.
Responsibility for attacks
Islamic Jihad claims responsibility for many of the attacks, although most of the projectiles fall without causing casualties.
Israel had accused al-Harazin of being one of the key leaders behind those attacks.
Al Jazeera's correspondent David Chater said analysts in Gaza believe that the Israeli raids make a mockery of the peace process that started in Annapolis and continued in Paris with Monday's aid conference.
He said Israel is holding back from a full-scale invasion into the Gaza Strip, mindful that it would not stop the rockets and mortars and would involve unacceptable casualties.
Israel has decided instead to hit harder at the cells responsible for the barrages, Chater said.
Ehud Barak, the Israeli defence minister, has told retired general Jim Jones, the recently appointed US envoy to the Middle East, that Israel must brace for the possibility of retaliatory attacks.
During their meeting at the Israeli defence ministry on Tuesday, which also included the military chief among other senior defence officials, Barak mapped out Israel's security priorities.
Meanwhile, Mahmoud Abbas, the Palestinian president, has denounced the Israeli raids.
At the same time, on Tuesday, he expressed support for a proposal for an international force to reinforce Palestinian security services.
Nicolas Sarkozy, the French president, called on Monday for a force to deploy in the Palestinian territories, "when the time comes and when the conditions are right" to "lend its support to the Palestinian security services".