Israeli warplanes fired missiles at five targets across Gaza overnight, killing a senior commander of the Hamas military wing and wounding 11 people, the group and the military said on Saturday.

The Israeli military said the strikes were in response to a powerful rocket fired from Gaza that hit the Israeli coastal city of Ashkelon on Friday. The attack caused damage but no injuries.

Gaza’s Islamic militant Hamas rulers said their slain member was Issa Batran, 42, a commander of the groups’ military wing in central Gaza and a senior rocket maker.

Batran had survived several previous Israeli attempts to kill him, but his wife and five of his children were killed during Israel’s three—week war in Gaza that ended in January 2009.

The cross—border violence came after weeks of relative calm and raised concerns of further escalation.

A Hamas spokesman said the militant group would avenge Batran’s killing.

“Hamas will not be quiet over the blood of its martyrs,” said Hamad al—Rakabi. “Israel is opening all the gates of fire. This blood will cascade into rage and fire,” al—Rakabi said.

Hamas says eight of its supporters and three civilians were also wounded in the overnight airstrikes.

The targets hit by missiles included a Hamas military training camp in Gaza City, smuggling tunnels under the Gaza—Egypt border and Batran’s shack on the outskirts of the Nusseirat refugee camp, Hamas security officials said.

The Islamic militants have been building crude rockets for the past decade, and have fired hundreds of them at Israeli border towns. However, the group has largely held its fire since Israel’s military offensive against Gaza ended 19 months ago.

There was no claim of responsibility for Friday’s rocket strike against Ashkelon, a city of 120,000 located 11 miles (18 kilometers) to the north of Gaza and a short drive from Israel’s main population centre in Tel Aviv.

Since Israel’s military offensive, small renegade groups in Gaza have occasionally fired crude short—range rockets. However, in Friday’s attack, Ashkelon was hit by a military—grade Grad rocket.

Hamas has ruled Gaza since seizing power in 2007, wresting control from their Fatah rivals of the internationally backed Palestinian President Mahmoud Abbas.

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