Updated

The Israeli military shelled Hamas targets in the Gaza Strip on Wednesday, killing three militants, after its troops on the border came under fire.

The army issued a statement saying it targeted Hamas military positions in the territory after a Palestinian sniper fired on Israeli soldiers "under the cover of 20 children that were sent towards the border fence as decoy." It military said an Israeli officer was moderately wounded.

Three Palestinians were killed in the Israeli artillery strikes near Gaza City, the Palestinian health ministry said.

A spokesman for the Hamas militant group, which rules the Gaza Strip, said the three were members of the Islamist organization's armed forces.

"The level of Israeli escalation against Gaza and the deliberate targeting of fighters demonstrate the occupation's intentions to kill," spokesman Fawzi Barhoum said. "We can't stay silent in front of the cruel and bloody Israeli occupation's leadership."

Hours after Wednesday's incident, air raid sirens sounded across communities in southern Israel.

The cross-border exchange took place a few days after Gaza's Hamas rulers agreed to a cease-fire with Israel to prevent weekend hostilities from escalating.

On Friday, a Palestinian sniper killed an Israeli soldier along the border — the first casualty Israel has sustained in four years — and Israel unleashed a heavy offensive in response. Israel and Hamas have fought three wars in the past decade.

These latest flare-ups of violence follow months of border protests organized weekly by Hamas. Over 130 Palestinians have been killed by Israeli gunfire since the protests began March 30.

The protests are aimed at ending the Israeli-Egyptian blockade of Gaza, put in place after Hamas took over the Gaza Strip in an armed coup in 2007. The blockade has brought severe economic hardship to the territory.

The protests also demand a "right of return" for descendants of Palestinian refugees to ancestral homes in what is now Israel. More than 700,000 Palestinians were expelled or fled during the 1948 Mideast war over Israel's creation, and two-thirds of Gaza's 2 million residents are descendants of refugees.