Terror groups opened fire at Israeli soldiers on the Gaza border on Wednesday, the sixth time in two days that Israelis have been targeted by gunfire or mortar rounds.

Both Hamas and Palestinian Islamic Jihad claimed responsibility for the attacks on the soldiers, who were originally engaged in operations aimed at finding Hamas tunnels. No Israelis were hurt.

Israel responded by shelling observation posts and other Hamas targets. Israel also sent messages to Hamas warning that they will execute a harsher response if mortar fire continues. “Our efforts to destroy the #Hamas terror tunnel network, a grave violation of Israel’s sovereignty, will not cease or be deterred,” IDF spokesman Lt. Col. Peter Lerner tweeted.

“This is the first time that Hamas has ordered an orchestrated attack against Israeli forces, which marks a change in policy, and unwanted escalation that might trigger the next conflict, ”Col. (res.) Eyal Rosen, the reserve commander of the IDF’s Gaza Border War Room Command Center, told reporters.

Monday’s mortar attack on IDF soldiers engaging in engineering work near the border fence was the first time a mortar shell was fired at IDF troops since Operation Protective Edge in the summer of 2014.

The IDF believes that the attacks are part of Hamas’ attempt to prevent the army from locating and destroying tunnels the terrorist group has built since the war’s end. Hamas surprised Israel and killed multiple Israeli soldiers through its use of cross-border tunnels during the war. While Israel largely destroyed the tunnels, Hamas has since invested heavily in rebuilding its network. Hamas reportedly spends hundreds of thousands of dollars each month and employs more than 1,000 operatives working 24 hours a day building tunnels. Haaretz defense analyst Amos Harel asserted in January that “It is reasonable to assume that the number of tunnels crossing under the border is close to that on the eve of Protective Edge.”

Last month, the IDF discovered a Hamas tunnel that crossed inside Israeli territory for the first time since 2014. Israel reportedly uncovered it using specialized new technology. “The prospect of an Israeli technology capable of detecting the tunnels thus threatens both its future achievements and its fighting ethos, which may be one reason for its renewed threats against Israel,” Harel wrote.

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