The Israeli air force struck 15 Hamas targets in three different locations in the Gaza Strip overnight Saturday, the Israel Defense Forces said. The operations were in response to rockets launched from Gaza, three of which were intercepted by Israel's Iron Dome anti-missile system. The rockets were the first violation of a cease-fire reached last week.

Rocket sirens were heard in various border communities in southern Israel throughout Saturday night and early Sunday. At around 1 A.M. Sunday, sirens sounded in the border town of Sderot and other communities followed by sirens in the Sha'ar Hanegev and Hof Asheklon regions hours later.

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At 1 A.M. early Sunday, the Israeli army announced that fighter planes had attacked three Hamas compounds, including two weapons-production and storage sites and another military compound. At around 6 P.M., the IDF reported another strike, this time at a site belonging to the Hamas naval force in the northern part of the strip.

The army said the operations were in response to rocket fire "and terrorist incidents led and made possible by the Hamas terrorist organization over the course of the weekend." These included the throwing of grenades and explosive charges, attempts to break through the Israeli border fence, damaging Israeli security infrastructure and setting fires on the Israeli side of the border through the use of kite-borne fire bombs and other incendiary devices, the army added.

Sources in Gaza said it is thought that the rockets were fired in response to Friday's killing of a 21-year-old Palestinian medic, Razzan Najjar, who was shot by Israeli army fire. Forty other Palestinians were wounded during demonstrations near the Israel-Gaza border on Friday, according to the Gaza Health Ministry. Najjar, a volunteer for a medical team helping wounded protesters, was shot near Khan Yunis. Thousands attended her funeral.

The Abu Arish Brigades claimed responsibility for the rocket fire. The organization, which is part of the Fatah-affiliated Al-Aqsa Martyrs Brigade, is a relatively small group whose power and capabilities are relatively limited.

Over the weekend, fires erupted at 20 sites on the Israeli side of the border. Israeli firefighting units attributed them in all probability to the kite bombs. The Israeli army also foiled an infiltration attempt on Saturday by a terrorist cell that attempted to get across the border fence from the southern Gaza Strip.

"Hamas is responsible for everything that happens in the strip and coming from it, including the serious attacks against the State of Israel and its citizens," the army said.

At least two mortar shells were fired from Gaza at Israel's Eshkol border region on Saturday evening, days after last week's most violent flare up since the 2014 war between Israel and Hamas ended in a cease-fire. The army said one mortar was intercepted by Israel's Iron Dome missile defense system while the other apparently fell on the Gaza side of the border. No casualties or property damage were reported.

On Sunday morning, the Palestinian Health Ministry reported the death of 30-year-old Mohammed Naim Hamada, who was shot and seriously wounded by Israeli forces near the Gaza border during mass protests on May 14. Hamada's death brings the Palestinian death toll in border clashes with the demonstrators to 120.

Last Wednesday, the Israeli army said it believed fighting in Gaza had come to an end and said it would respect the calm if Hamas ended the rocket fire towards Israel. Hamas agreed to accept a unilateral cease-fire after talks with Egypt, despite the fact the Israel was not party to the talks.

Since the confrontations along the border of May 14, the number of participants in border demonstrations has fallen dramatically. Hamas and other Palestinian factions have set June 5, this Tuesday, as the date for a march by tens of thousands to mark 51 years since the Six-Day War.