A barrage of at least 50 rockets from the occupied Gaza Strip struck southern Israel, Israeli police have said, a day after Israeli forces killed three Palestinian fighters in the enclave.

There were no immediate reports of casualties after the rockets hit on Wednesday, mainly around Sderot. "It's a barrage such as we haven't seen for two years," a local official said on Army Radio.

The Palestinian armed group, Islamic Jihad, claimed it had fired more than 130 rockets and mortar bombs, although this figure was not verified.

"The al-Quds Brigades responded to aggression with a volley of rockets," the group said in a statement, calling the operation "Breaking the Silence" and vowing more attacks.

In response, Israeli artillery was reported to have hit launch sites inside Gaza. Residents of Beit Hanoun said they saw Israeli fire hit one site nearby.

Israeli jets also attacked Islamic Jihad training camps around Rafah, which had already been cleared by the group, a source told Al Jazeera.

The Israeli prime minister, Benjamin Netanyahu, on Wednesday vowed to continue striking Gaza rocket launcher squads.

"We will continue to thwart and hit those that want to harm us, and we will act against them with great force,'' he said.

The Hamas group, which controls Gaza, said it would hold Israel responsible for any escalation.

"We hold the occupation responsible, we warn of the consequences of any escalation and we reiterate that resistance is the right of the Palestinian people to defend itself," said Ihab al-Ghassin, a spokesman for Hamas.

The rocket salvos come a day after an Israeli airstrike killed three Islamic Jihad members, who Israel claimed had fired mortar bombs at Israel.

Israel pulled its troops and settlers out of the now-Hamas-run territory in 2005. But it maintains a naval and air blockade and severely restricts the overland movement of people and goods across the volatile border.