At least seven Palestinian civilians have been killed in Israeli shelling in the Gaza Strip.
Israeli artillery shells slammed into a Gaza beach and scored a direct hit on a Palestinian family at a picnic.
Palestinian officials say three children were among the dead, including twins.
Israeli canons and gunboats have been shelling areas used by Palestinian militants who have been firing rockets at Israel for weeks. The army says some shells apparently went astray.
"We have no intention of harming innocent civilians and we are very sorry about it," Galant told Israel Television. "But at the same time," he said, "we have a duty to defend the citizens of Israel from rocket attacks," said General Yoav Galant, head of Israel's Southern Command.
The incident is further escalating tensions after Israel assassinated a top Palestinian security chief appointed by the new government of the Islamic militant group Hamas. Jamal Abu Samhadana and three other militants were killed in an Israeli air strike that Hamas described as a direct attack on the Palestinian Authority.
"The Palestinian people have the right to defend themselves," said Prime Minister Ismail Haniyeh. The Hamas military wing went a step further, vowing to resume suicide bombings in Israeli cities. If that happens, it would mean an end to the truce declared by Hamas 16 months ago, and a new round of bloodshed.