Hamas militants in Gaza have fired dozens of rockets into southern Israel.

The Islamist movement said it had fired the rockets after six of its men were killed in Israeli air strikes.

The bombardment was confirmed by the Israeli army, which said militants had launched "a few dozen rockets" within a short period of time.

At least four were intercepted over Netivot by the Iron Dome anti-missile system, while another 16 struck the area around the southern city of Be'er Sheva, which is 40km from Gaza and home to 200,000 people.

Media reports put the number of rockets at around 40, but there were no reports of casualties.

The rocket fire was claimed by Hamas's armed wing, the Ezzedine al-Qassam Brigades, in a statement sent to the AFP news agency in Gaza.

"Al-Qassam fired dozens of rockets on Netivot and Ashkelon, Ashdod and Ofakim in response to the Zionist aggression," the group said.

The rocket fire came several hours after Israel staged around 16 air strikes on targets across Gaza, following a night in which planes had attacked 14 targets, killing at least three militants.

Another five Hamas militants died and one was left in critical condition when a tunnel collapsed near the southern city of Rafah, with the movement blaming it on an Israeli air strike.

The Israeli army denied hitting the area where the tunnel was, with a spokesman describing it as a work accident by militants handling explosives.