Israel and Hamas fighters are still trading fire in Israeli towns a day after the Palestinian militants breached the heavily fortified border from Gaza and poured into nearby settlements, killing and taking hostage both soldiers and civilians in an unprecedented attack.

British citizen Jacob Marlowe is among the missing after Hamas stormed a music festival and seized partygoers as hostages on Saturday morning.

The death toll for Israelis has risen to almost 600, several local media outlets have reported including Times of Israel and Haaretz.

Vowing brutal retaliation, Israeli prime minister Benjamin Netanyahu has declared the country to be at war and vowed to turn Hamas sites to rubble – warning Palestinians they should leave besieged Gaza, despite them being unable to do so.

Gaza health authorities reported 313 fatalities, as relentless Israeli strikes continued overnight. Israel’s military claimed on Sunday to have killed more than 400 Hamas gunmen as battles continued to dislodge and root out militants from eight settlements within Israel.

The military gave Israeli residents 24 hours to evacuate homes near the border, warning that “every attacker located in a house, all the commanders in houses, will be hit by Israeli fire”.