Four Israeli soldiers have been hurt, two of them seriously, in an explosion near the Israeli-Gaza border.
The army said a Palestinian flag was flying in the area, and when the troops approached they were hit by the blast.
In response, Israel conducted air strikes against Hamas targets in Gaza. There were no reports of casualties.
Israeli media are describing the blast as the worst incident on the border since Israel and Hamas militants, who dominate Gaza, fought a war in 2014.
No group has so far said it was behind the explosion.
The incident happened at 16:00 local time (14:00 GMT) east of the town of Khan Younis.
The army said the explosive device had been planted during a demonstration there on Friday and was attached to a flag.
The troops were approaching from the Israeli side when the device detonated.
Israeli Prime Minister Benjamin Netanyahu, who is attending a security conference in Munich, Germany, said: “The incident on the Gaza border is very serious. We will respond appropriately.”
Palestinian officials said three Hamas training camps and one belonging to a smaller group had been struck but no-one was injured.
Israeli media also said a rocket from Gaza fell near a house in the south of the country on Saturday evening. There were no casualties.
Israel holds Hamas responsible for all rocket and mortar fire from the territory. Hamas has fought three wars with Israel since 2008.
Correspondents say the border area has been generally quiet in the last few years but there has been an increase in violence since US President Donald Trump’s announcement in December recognising Jerusalem as Israel’s capital.
Israel regards Jerusalem as its indivisible capital. Palestinians want the east of the city, which Israel occupied in the 1967 Middle East war, to be a capital of a future state.
Authorities arrested a 31-year-old man who allegedly shot and killed a 4-year-old girl in a domestic dispute in Akron, Ohio.
Darnell Bitting is charged with murder and using weapons under disability in the shooting, which took place outside of a home Friday evening, according to police.
Officers responded to a shooting on the 900 block of Mercer Avenue Friday.
Four children — ages 7, 6, 4, and 3 — were seated inside a car with their grandmother.
The children’s mother told police she had visited the house to retrieve her belongings. No one answered the door and she broke out some of the home’s windows, police said.
A man with a rifle emerged from the residence and fired at the car.
The grandmother, who was in the passenger seat, climbed into the driver’s seat and drove away from the home, but not before the 4-year-old was struck by a bullet.
She was taken to a local hospital where she was pronounced dead.