The air raids hit targets in the southern city of Rafah, in the northern town of Jabaliya and also struck a site which had been previously been used for launching rockets in the Zeitun district, just east of Gaza City, they said.

The army had no immediate comment on the raids which took place hours after a mortar shell was fired into southern Israel.

Tensions have been rising along the Israel-Gaza border in recent months, with militants firing dozens of rockets and mortar rounds into southern Israel and the air force responding with strikes targeting training sites, weapons facilities and smuggling tunnels.

On Wednesday, Palestinian militants had fired seven projectiles, most of them mortar shells, across the border without causing any injuries or damage, the army said.

And overnight, Israeli troops shot dead two Palestinians whom they said were trying to get across the border fence into Israel.