GAZA CITY, Palestine: Two Palestinians were killed and another injured in an explosion in Gaza City Tuesday night, the Palestinian health ministry said, adding the cause of the blast was unknown.

The Israeli military denied the deaths was caused by one of its air strikes, and Palestinian eyewitnesses at the scene told AFP they had seen no aircraft overhead.

Earlier on Tuesday, Israel had launched an air strike against Gaza’s Hamas rulers on Tuesday after its militants in the strip fired a mortar round across the border, the army said.

Witnesses said 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 Defense 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 defense 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 cease-fire.

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