The Israeli air force carried out four strikes on militant targets in the Gaza Strip early Wednesday, Palestinian eyewitnesses said, hours after a cross-border rocket attack on the Jewish state.

The planes targeted training camps belonging to the Islamic Jihad in Rafah, Khan Yunis and Gaza City, the witnesses said. There were no immediate reports of casualties.

Late Tuesday a rocket fired from the Palestinian enclave struck southern Israel, causing no casualties or damage.

The Israeli army said it struck "four terror infrastructures in the southern Gaza Strip" in response to the rocket attack.

"The reality that Hamas's territory is used as a staging ground to attack Israel is unacceptable and intolerable and will bear consequences," military spokesman Lieutenant Colonel Peter Lerner said in a statement.

Islamic movement Hamas, which de facto rules Gaza, has not assumed responsibility for the attack.

Tuesday's rocket was the third fired from Gaza since the ceasefire ending the 50-day conflict in summer 2014, which killed about 2,200 Palestinians, most of them civilians, and 73 on the Israeli side, most of them soldiers.

Two mortar bombs were also fired at Israel since September, according to the Shin Bet internal security agency,

Wednesday's air strike was the third since the end of the 2014 war.

Last month, tanks fired at a Hamas position following a rocket attack.