An Israeli airstrike in Gaza on Friday killed the commander of the militant group behind the abduction of Gilad Schalit, an Israeli soldier who was held captive for more than five years and freed in a prisoner swap for more than 1,000 Palestinians.

The midday attack marked the highest profile Israeli strike against the coastal strip in several months and immediately set off a violent escalation after a period of relative calm.

Various Palestinian militant groups fired dozens of rockets, some deep into Israeli territory, prompting Israel to issue warnings to its residents to stay indoors. The Israeli military pounded several rocket launching cells in Gaza. In all, nine Palestinian militants were killed in airstrikes, and one Israeli citizen was seriously wounded by the Palestinian rocket fire.

Zuhair al-Qaissi, seen in 2011 file photo, was plotting an infiltration attack similar to one his group carried out in August that killed eight Israelis, the Israeli military said. (Hatem Moussa/Associated Press)

The Israeli military said it initially targeted Zuhair al-Qaissi, the commander of the armed wing of the Popular Resistance Committee, a large militant group closely aligned with Gaza's Hamas rulers. The explosion tore apart al-Qaissi's blue sedan and killed his son-in-law, Mahmoud Hanini, himself a top PRC field commander. Another low ranking Gaza militant also died.

Hours later, Israeli military killed two more militants that it said were about to launch rockets. After midnight, Palestinian officials said another four were killed in and around Gaza City.

Palestinian witnesses said Israeli drones were seen hovering above just moments before al-Qaissi's vehicle burst into flames. They said the blast was so fierce that al-Qaissi's head detached as a result.

Al-Qaissi was the top commander of the armed wing of the Popular Resistance Committee, a large militant group aligned with Hamas that was behind the 2006 abduction of Schalit, an Israeli soldier who was held in Gaza for more than five years until he was freed in a prisoner swap last year. The Israeli military said that al-Qaissi was behind several deadly attacks against Israel, including rocket fire, and he was also in charge of transferring funds from the Lebanese militant group Hezbollah to other militant groups in Gaza.

The PRC's spokesman confirmed al-Qaissi's death, and identified the second casualty as Mahmoud Hanini, who hails from the West Bank and was released from an Israeli prison five years ago and deported to Gaza.

'We shall avenge our leader and the response, God willing, will be equal to the size of the heinous crime.'— Abu Mujahid, Popular Resistance Committee

"The coward Zionists have committed an ugly crime, and they know the price that they are going to pay," said the spokesman, who goes by the pseudonym Abu Mujahid, suggesting retaliation could be on the way. Such strikes often lead to return rocket strikes from Gaza into Israel.

"We call on our fighters to respond to the Zionist enemy with all our strength," he said. "We shall avenge our leader and the response, God willing, will be equal to the size of the heinous crime."

The Israeli military insisted it did not want an escalation but said it was "prepared to defend the residents of Israel." It charged that Hamas was using other groups to carry out attacks and "will bear the consequences of these actions" if an escalation takes place.

Israel often targets Gaza militants it says are preparing attacks, but tensions have been relatively calm in recent months with Israel mostly targeting smuggling tunnels from Egypt and refraining from targeting individuals. Al-Qaissi, who is also known as Abu Ibrahim, is the highest profile casualty in Gaza in months.