Jerusalem (CNN) -- Four Palestinian fighters were reported killed in clashes with the Israeli military in Gaza early Friday as the Israelis destroyed what they said were two "terror tunnels" there.
Four fighters with the al Qassam Brigades -- the military wing of Hamas, which controls Gaza -- were killed in the incidents, the militant group's website said. Israel said five of its soldiers were injured.
One of Israel's targets was a tunnel, discovered on October 7, that the Israeli military said reached from Gaza into Israel and might have been intended to help Palestinian militants kidnap Israelis.
Israeli military engineers early Friday detonated a segment of that tunnel, which it said stretched 1.7 kilometers (1.06 miles) from Gaza into Israel, near Israeli communities.
As that happened, Hamas fighters detonated an explosive, injuring five Israeli soldiers, the Israeli military said. Israeli soldiers then opened fire and "directly hit a terrorist," it said.
That appears to match what the medical service in Gaza said was the death of a man around midnight Thursday or early Friday along the Gaza-Israel border, east of the southern Gaza Strip city of Khan Younis. The man was hit by an Israeli tank shell, said the medical service's spokesman, Ashraf Qidra.
The al Qassam Brigades' website said that man was one of its fighters. Al Qassam's Twitter account described the clash as an ambush in which its fighters seriously injured five Israeli soldiers.
The Israeli military said it also used aircraft to destroy a second "terror tunnel" in the southern Gaza Strip on Friday "following Hamas aggression."
Israel didn't give specifics about the second tunnel. But the al Qassam Brigades said Israeli helicopters and tanks fired on and killed three of its fighters north of Khan Younis.
Qidra, the Gaza medical services spokesman, said the bodies of those three were not immediately recovered.
Israeli military spokesman Lt. Col. Peter Lerner said the mission was imperative to prevent "future attacks against Israeli civilians."
The first tunnel destroyed, he said, was similar to one that was used to kidnap Israeli soldier Gilad Shalit in June 2006. His captivity ended five years later, after Israel released more than 1,000 Palestinian prisoners.
The tunnel discovered on October 7 was the third such tunnel found along the Gaza-Israel security fence in the past year, according to the Israeli military.
The Israel Defense Forces said Friday that Hamas' "offensive actions against Israel" breached cease-fire arrangements reached after last year's "Pillar of Defense" operation.
In that November 2012 operation, Israel launched a series of military strikes on Gaza designed to stop constant rocket fire. Eight days of round-the-clock warfare followed between Israel and Hamas. More than 160 Palestinians, many of whom were civilians, were killed. Six Israelis died, including civilians and soldiers. Hundreds were wounded.
Friday's clashes come two days after Israel released 26 Palestinian prisoners, part of an agreement that fueled new peace talks. The Palestinian Prison Authority confirmed that 21 prisoners were released early Wednesday in the West Bank and five others were released in Gaza.
The released prisoners were the second of four groups -- roughly 100 prisoners -- expected to be freed in a deal cobbled together by the United States to jump-start stalled Israeli-Palestinian peace talks.
CNN's Jason Hanna and Matthew Chance contributed to this report.