An Israeli air strike wounded two Palestinians near the Gaza border on Tuesday, prompting retaliatory rocket fire by Hamas militants, the army and witnesses said.
The military wing of Hamas, which controls the Gaza Strip and generally maintains a tacit truce with Israel, made a rare claim of responsibility for the pre-dawn rocket fire.
Witnesses said that two men were injured in an air strike shortly after midnight (2100 GMT) near the frontier east of the Gaza town of Deir el-Balah, and taken by troops into Israel.
The army confirmed hitting what it called a "terrorist squad identified handling an explosive device near the security fence in the central Gaza Strip," but a spokeswoman denied that wounded men were brought across the border.
Before dawn, four rockets from Gaza slammed into southern Israel's Hof Ashkelon district but caused no casualties or property damage, the army said.
A statement from the Ezzedine al-Qassam Brigades, the military wing of the Islamist Hamas, said that it fired the rockets in response to "Israel's crimes."
On Monday Israeli aircraft killed four Palestinians in two sorties over the northern Gaza town of Beit Hanun, and wounded at least three, Palestinian medics said.
Ezzedine al-Qassam Brigades said one of those killed was a member of the group.
The military said that he was part of "a terrorist squad attempting to fire a rocket at Israel."
Monday's strikes came hours after gunmen had mounted an early morning deadly ambush along Israel's southern border with Egypt, killing an Israeli civilian construction worker. Two of the gunmen were shot dead by Israeli troops.
An Israeli military source insisted however that Monday's air strikes were not related to the ambush.
Israeli media reported that workmen were on Tuesday back at the scene of the attack as well as at other construction sites along the route of the fence.
On Monday afternoon, the army said, a rocket was fired from Gaza into the Hof Ashkelon area and another fell at night.
"Altogether six rockets were fired in the past 24 hours," a spokeswoman told AFP on Tuesday morning.