Israeli forces unleashed a wave of strikes across the Gaza Strip on Friday after saying its troops came under fire, killing three Hamas members as fears grew of a wider conflict.
A fourth Palestinian was also shot dead during protests along the frontier with Israel, Gaza’s health ministry said.
Israeli Defence Avigdor Lieberman warned of a “much tougher” response to any fresh missile fire by Hamas after the army reported “three launches” from the territory, two of which were intercepted.
The United Nations envoy for the Middle East peace process, Nickolay Mladenov, said “everyone in Gaza needs to step back from the brink. Not next week. Not tomorrow. Right NOW!”
“Those who want to provoke Palestinians and Israelis into another war must not succeed,” he wrote on Twitter.
The Israeli army said aircraft and tanks struck back after troops came under fire during renewed protests along the Gaza-Israel frontier.
Spokesman Jonathan Conricus called the shooting incident a “very severe event”, but said he could not divulge full details.
“The attack today… was a severe one, one that we cannot tolerate,” he said, dadding that sniper fire and grenades had been directed at soldiers on the border.
The military wing of Islamist group Hamas, which has fought three wars with Israel since 2008, said three of its fighters were killed in strikes.
Air raids were continuing into the evening, with a number of explosions in different parts of Gaza, correspondents said.
Israel’s military said its aircraft and tanks targeted “eight military posts” belonging to Hamas and that the strikes formed part of a “wide-scale attack”.
“Hamas chose to escalate the security situation and will bear the consequences for its actions,” the military warned.
– ‘Emergency briefing’ –
Israeli media reported Prime Minister Benjamin Netanyahu was receiving an emergency briefing from the army on the situation.
Last weekend saw the most severe exchange of fire between Israel and Palestinian militants in Gaza since a 2014 war.
Israel hit dozens of sites it said belonged to militants in the Gaza Strip in Saturday’s strikes, killing two Palestinian teenagers.
The same day, around 200 rockets and mortars were fired at Israel from Gaza and four Israelis were wounded when a rocket hit a house in the nearby Israeli city of Sderot.
Since protests broke out on March 30, at least 149 Palestinians have been killed.
Most were shot during demonstrations and clashes along the border, but others were killed in air strikes or by tank fire.
No Israelis have been killed.
For more than a week, Israel has been hardening its response to kites and incendiary balloons launched from Gaza, which authorities say have set ablaze more than 2,600 hectares (6,400 acres) on Israeli territory.
In recent days, the Israeli army has opened fire at groups launching such devices.
Lieberman has raised the threat of a large-scale operation in the Gaza Strip if Hamas does not stop the kites and balloons being launched.
Israeli television this week broadcast footage of army training manoeuvres for an incursion into the Gaza Strip.
Netanyahu also toured the border region for the first time since the start of the clashes.
Government officials such as Education Minister Naftali Bennett and Internal Security Minister Gilad Erdan have called for systematic attacks on kite launchers.
Israel has also further tightened its blockade of Gaza by closing the only goods crossing, suspending oil and gas deliveries.
Prasanta Patnaik 
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