Hamas says it does not know the whereabouts of an Israeli soldier it had been accused of capturing in Gaza.
The Islamist group's military wing says it lost contact with some fighters in the area and that they and Hadar Goldin, 23, may have been killed.
His supposed capture and the violence that followed ended a 72-hour ceasefire just hours after it had begun.
Earlier, US President Obama described the crisis as "heartbreaking" and said he would work to secure another truce.
"Innocent civilians caught in the crossfire have to weigh on our conscience," he said, but added that Hamas had to show it was serious about wanting an end to the violence.
Israeli airstrikes continued into the early hours of Saturday morning, with Gaza health officials saying nearly 100 Palestinians had been killed following the collapse of a ceasefire.
At least 1,600 Palestinians, mostly civilians, have now died, and 8,400 have been injured, according to Gaza's health ministry.
Sixty-one Israeli soldiers have died, as well as three civilians in Israel.
Hamas accused Israel of breaking the short-lived ceasefire but the Israel Defense Forces (IDF) said it had been forced to respond to militant rocket fire.
Shortly after the ceasefire ended, IDF spokesman Lieutenant Colonel Peter Lerner said "initial indications suggest a soldier has been abducted" during an ambush on Israeli troops.
Two other soldiers were killed after a suicide bomber blew himself up during the ambush, he added.
President Obama described the capture of the soldier as "barbaric" and Israel said its response would be "crushing".
But in a statement released early on Saturday, the Qassam Brigades, Hamas' military wing, said it had "no information on this soldier".
It said it lost contact with a group of fighters in the area where the IDF soldier went missing, saying: "We believe they were all killed in the [Israeli] bombardment.
"Assuming that they managed to seize the soldier during combat, we assess that he was also killed in the incident."
There were also clashes in the West Bank on Friday as thousands of Palestinians took to the streets to protest against Israel's offensive in the Gaza Strip.
Two Palestinian protesters were shot dead in separate incidents after violence got out of control, an IDF spokeswoman said.
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