The Israeli air force has carried out four strikes on targets in the besieged Gaza Strip hours after a cross-border rocket landed in the city of Ashdod.

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

Earlier on Tuesday, the Qassam Brigades, the military wing of the Palestinian group Hamas, confirmed that they had fired five experimental rockets into the sea, but one of them had landed by mistake in the southern Israeli city.

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

"The reality that Hamas' 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.

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

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

Wednesday's air strikes were the third since the end of the 2014 conflict.

Source: Al Jazeera and agencies