Witnesses in the coastal enclave told AFP that fire from an Israeli drone hit Hamas facilities east of Al-Bureij refugee camp.

No injuries were reported.

"A short while ago a mortar shell was identified as having been fired from the Gaza Strip into Israeli territory," an Israeli army statement said in English.

"In response, an Israel Defence Forces aircraft targeted a Hamas military post in the northern Gaza Strip."

Israeli media said the shell fell on open ground, causing no injuries or damage.

Tuesday's events were the latest in a string of cross-border incidents which have raised concerns of further escalation before Israel's September 17 elections.

On Monday Israeli warplanes hit what the military said were "terror targets in a Hamas military compound in the northern Gaza Strip, including the office of a Hamas battalion commander."

Israel also announced it was slashing by half the fuel it pipes to the strip's main power station, meaning a cut to Gaza's already meagre electricity supply.

The measures came after three rockets were fired from Gaza into southern Israel on Sunday night, according to the army, which said two of them were intercepted by air defence systems.

Israel and Palestinian militants in Gaza have fought three wars since 2008.

August has seen rocket fire from Gaza, infiltration attempts by armed Palestinians and return fire by Israel, threatening a fragile ceasefire.

Israeli prime minister Benjamin Netanyahu is fighting for reelection in the September polls, with political opponents calling for tougher action against Islamist movement Hamas.