The strikes hit what the military described as "terror targets" operated by Gaza's Islamist ruling party Hamas.

They included a "training facility, an anti-aircraft missile launcher post, a concrete production plant & terror tunnel infrastructure".

Witnesses and security sources said the strikes hit two militant "training sites" in southern Gaza and another target in central Gaza.

A Hamas spokesman said that despite the Israeli action, "Gaza still fights and doesn't break."

The strikes came hours after militants in the Gaza Strip fired a rocket into southern Israel.

An Israeli army spokesperson said the rocket hit open ground and caused no casualties or damage.

It was the second such exchange in recent days. Late Thursday, Palestinian militants fired a rocket at southern Israel, prompting the army to launch retaliatory air strikes on Gaza that caused no casualties.

Israel imposed a blockade of Gaza's sea and land borders after Hamas seized control in 2007. The two sides have since fought three wars.

A fragile truce has endured in recent years despite occasional flareups, with Palestinians firing rockets at Israel and the Jewish state responding with airstrikes on the coastal enclave.