Gaza's militant Hamas rulers threatened to escalate fighting with Israel on Saturday after airstrikes killed several gunmen in the coastal territory, and Palestinian rocket attacks on Israel wounded one person and damaged an elementary school in the country's south.

The two sides periodically clash, but this flare-up was the most serious in months. It started with an attack by a little known al-Qaida-inspired Palestinian militant group but has extended to drag in Hamas.

Hamas has largely stayed out of direct confrontation with Israel since a war more than three years ago although other factions have launched cross-border attacks.

Gaza militants fired over 30 rockets and mortar shells on Saturday alone, bringing the week's rocket tally to more than 150, according to the Israeli military.

Over a million people in southern Israel live in range of the rockets and the Israeli military has advised the residents to make sure they can get to a bomb shelter quickly.