Israeli F-16 fighter jets launched a series of airstrikes on the Gaza Strip at dawn Thursday, shortly after Palestinian militants fired rockets into southern Israel.

Witnesses told Xinhua that there were at least four powerful blasts in Gaza City.

Palestinian security sources said two of the airstrikes targeted training sites of the Hamas movement, which controls the coastal enclave. Another jet dropped a bomb on an open space in east Gaza.

Initial updates from Hamas' ministry of health said that at least two residents living near the targeted sites were injured. The ministry's spokesperson was not immediately available for giving details.

The Israeli raids came a few hours after militants fired several rockets toward the coastal city of Ashkelon in southern Israel.

Israeli media said that Iron Dome missile defense system intercepted five of the rockets and the sixth was believed to have landed in an open field.

No Palestinian group has claimed responsibility for the rocket attack yet.

Palestinian factions in Gaza, led by Hamas, hold a fragile ceasefire with Israel. However, there are often reports of tit-for-tat attacks on the two sides of the volatile fence.