By Jodi Rudoren and Isabel Kershner

New York Times News Service

JERUSALEM — Palestinian militants sprang from the ground and confronted Israeli soldiers Friday morning, as they have repeatedly in recent days. This time, Israeli officials said, one exploded a suicide belt while another unleashed machine-gun fire. This time, two Israeli soldiers were killed and the militants apparently escaped with a third.

The attack, at the start of what was supposed to be a 72-hour pause in the fighting, escalated the deadly 25-day battle between Israel and Hamas, the Islamist faction that dominates the Gaza Strip.

Israel said the attack from under a house near the southern border town of Rafah took place at 9:20 a.m., soon after the 8 a.m. onset of the temporary truce secured by the Obama administration and the United Nations, whose leaders squarely blamed the breakdown on Hamas.

Hamas’ account was confused. One leader was quoted claiming credit for the abduction, then backtracked. Others contended that the clash unfolded at 7 a.m., before the cease-fire, although Palestinian reports of fighting near Rafah came three hours later.

What was clear was that the episode dimmed prospects for curtailing a conflict that has killed more than 1,600 Palestinians, many of them women and children, and plunged Gaza into a humanitarian crisis. Israel responded with an aggressive assault that killed 70 people and injured 350 around Rafah alone as troops sealed the area to hunt for the missing officer amid mounting pressure from Israeli politicians and the public to expand the military mission.

The events renewed command-and-control questions about Hamas, a guerrilla group torn by rivalries and communication snags between its military and political rulers in Gaza and abroad. They also suggested neither side is ready for an exit ramp until its goals are met: for Israel, destruction of the tunnels and a halt to rocket fire from Gaza, and for Hamas, a score that can be leveraged to change the social and economic conditions of Gaza’s 1.7 million beleaguered people.

“It’s going to be very hard to put a cease-fire back together again if Israelis and the international community can’t feel confident that Hamas can follow through,” President Barack Obama said Friday at the White House.

Both Secretary of State John Kerry and Ban Ki-moon, the secretary-general of the United Nations, demanded an immediate and unconditional release of the Israeli officer. Ban described the attack as “a grave violation of the cease-fire” that called “into question the credibility of Hamas’ assurances to the United Nations.”