Israeli forces killed four Palestinians in Rafah in the southern Gaza Strip on Monday after they emerged from an underground tunnel and opened fire on troops, Israel’s military said.

It described the attack as a violation of the US-brokered ceasefire with Hamas that went into force in Gaza last October that it viewed with the “utmost gravity”.

There was no immediate comment from Hamas, but some sources close to the group identified one of those killed as Anas Annashar, the son of senior Hamas official and co-founder Issa Annashar.

Israel has responded to similar incidents in recent months by carrying out airstrikes across the enclave in which dozens of people have been killed.

Later on Monday, an Israeli airstrike killed three Palestinians in an apartment in Gaza City, north of the enclave, health officials said.