GAZA CITY, Gaza Strip - Backed by tank fire and airstrikes, Israeli forces pushed deep into southern Gaza on Friday, searching for an Israeli army officer believed to be captured by Hamas fighters during deadly clashes that shattered an internationally brokered cease-fire.
The apparent capture of the soldier and the collapse of the truce set the stage for a possible expansion of Israel's 25-day-old military operation against Hamas.
President Barack Obama and U.N. chief Ban Ki-moon called for the immediate release of the soldier but also appealed for restraint. In Israel, senior Cabinet ministers convened late Friday in a rare emergency meeting after the start of the Jewish Sabbath.
Israeli Merkava tanks drive through trees in southern Israel as they advance towards the Israel Gaza border, Friday.
The search for the missing soldier centered on the outskirts of the town of Rafah, on the Egypt-Gaza border.
At least 140 Palestinians were killed Friday in Gaza, with at least 70 killed in the Rafah area along with two Israeli soldiers.
Earlier Friday, Israel and Hamas accused each other of breaking the truce, which had been announced by the U.S. and the U.N., and took effect at 8 a.m.
The breakdown meant there would be no reprieve for the 1.7 million residents of Gaza, where large parts have been devastated by airstrikes and shelling, and at least 1,600 people - mostly civilians - have been killed and more than 8,000 wounded. Israel has lost 63 soldiers and three civilians.
The fighting in the Rafah area continued into the night, with residents reporting airstrikes along the Egypt-Gaza frontier as well as heavy tank and artillery shelling. The Israeli military said it was searching for the missing soldier and had sent automated calls or text messages to Rafah residents to stay indoors.
"We are under fire, every minute or so tanks fire shells at us," said Rafah resident Ayman Al-Arja. "I have been thinking of leaving since 2 p.m., but tank fire can reach anywhere, and I was scared they will hit my pickup truck. Now we are sitting in the stairwell, 11 members of my family, my brother, his nine children and wife. We just have water to drink and the radio to hear the news."
The 45-year-old Al-Arja added: "We are just staying put waiting for God's mercy."
The heavy shelling in Rafah was part of operational and intelligence activity to locate the missing officer, 2nd Lt. Hadar Goldin, the Israeli military said.
An hour after the cease-fire began, gunmen emerged from one or more Gaza tunnels and opened fire at Israeli soldiers, with at least one of the militants detonating an explosives vest, said Israeli army spokesman Lt. Col. Peter Lerner.
Goldin, a 23-year-old from the central Israeli town of Kfar Saba, was apparently captured in the ensuing mayhem, while another two Israeli soldiers were killed.
"We suspect that he has been kidnapped," Lerner said.
Obama called for Goldin's unconditional and immediate release and said it would be difficult to put the cease-fire back together. However, he said the U.S. will continue working toward a cease-fire.
He said Israel committed to the truce, but at the same time called the situation in Gaza "heartbreaking" and repeated calls for Israel to do more to prevent Palestinian civilian casualties.
"Innocent civilians caught in the crossfire have to weigh on our conscience, and we have to do more," Obama said. He added that Israel must be able to defend itself, but that irresponsible actions by Hamas have put civilians in danger.
Israel has gone to great lengths in the past to get back its captured soldiers. In 2011, it traded hundreds of Palestinian prisoners for an Israeli soldier who had been captured by Hamas-allied militants in 2006. The capture of two soldiers in a cross-border operation by Lebanon's Hezbollah guerrillas in 2006 sparked a 34-day war between the Iranian-backed Shiite group and Israel.
A Hamas spokesman, Fawzi Barhoum, would neither confirm nor deny the capture, saying the event was being used - along with the killing of two Israeli soldiers in the Rafah area - as a cover for what he called a "massacre" in Rafah.
The violence killed at least 70 Palestinians and wounded 440 in the Rafah area, according to Gaza Health Ministry official Ashraf al-Kidra. The dead included paramedic Assef al-Zamily, killed when an Israeli tank shell hit an ambulance in which he was riding, al-Kidra said.