The military said all four were evacuated for medical treatment. In response, the military said one of its tanks struck an observation post in the southern Gaza Strip. Palestinian officials said the target belonged to the Islamic Jihad militant group and that there were no casualties on the Palestinian side.
Israel typically strikes Hamas, the Islamic militant group that rules Gaza, for all attacks emanating from the territory, regardless of who carries them out.
In the post 2014 war reality established along the volatile frontier, Israel generally carries out limited retaliations to any militant provocations in Gaza. The border area has generally been quiet since the war, but has seen an increase in violence since President Donald Trump's announcement in December recognizing Jerusalem as Israel's capital.
However, any Israeli casualties could spark a fiercer Israeli response. Israeli Prime Minister Benjamin Netanyahu called the incident "severe" and vowed to "respond accordingly."
Later, Gaza officials reported a series of Israeli airstrikes against empty militant training sites. No casualties were reported.
Saturday's incident comes amid rising warnings of a brewing humanitarian disaster in Gaza that Israel fears could spill over into violence.
Gaza, a tiny strip of land sandwiched between Israel and Egypt, has seen conditions steadily deteriorate. Hamas won legislative elections in 2006 and forcibly seized the territory the following year from the internationally backed Palestinian Authority. Israel and Egypt imposed a blockade in an attempt to weaken Hamas, and Israel and Hamas have fought three wars. Palestinian President Mahmoud Abbas, hoping to regain control, has stepped up pressure on Hamas by cutting salaries of civil servants and limiting electricity deliveries.
Israel, however, has begun to soften its line of late, appealing for international aid, and may be less inclined to strike hard militarily, even if targeted by rocket fire and border attacks.
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