Footage filmed in Khan Younis in the south of the enclave showed three large explosions, while fighter jets could be heard flying overhead.

There was no immediate confirmation on whether there were any casualties.

The Israeli military said they had targeted a Hamas rocket manufacturing facility and a military post in retaliation for two rockets being fired from Gaza on Saturday, landing in the Mediterranean Sea off central Israel.

Whether the rockets were meant to hit Israel is unclear, but Hamas often test-fires missiles towards the sea.

There were no casualty reports from Saturday's launches.

A ceasefire brokered by Egypt and other mediators following an 11-day war between Israel and Hamas in May has almost held up until now, apart from a single incident in September.

The ceasefire has been fragile, with Hamas saying Israel did not take enough steps to ease the blockade it imposed on Gaza with Egypt's help when Hamas seized control of Gaza in 2007.

Other groups have added tension to the situation, including the smaller but more hardline Islamic Jihad group - which has threatened military escalation if Israel does not end the detention of a Palestinian prisoner who has been on hunger strike for more than 130 days.

On Wednesday, Palestinian militants in Gaza shot and injured an Israeli civilian near the security fence. Israel then targeted several Hamas sites with tank fire in the first exchange of fire in months.