JERUSALEM (CNN) -- A truce in Gaza that was supposed to last three hours on Wednesday failed after just 15 minutes.
Flames rise into the sky after an Israeli airstrike Wednesday night in Rafa, on the Gaza-Egypt border.
The suspension of the campaign from 1 p.m. until 4 p.m. was intended to allow residents of the Hamas-ruled Palestinian territory to receive food and medical supplies.
Israeli forces fired at militants in Gaza after Hamas militants targeted Israeli forces "almost immediately at 1 p.m.," according to Israeli Defense Ministry spokesman Peter Lerner.
Lerner had previously said Israeli forces would respond to any aggression directed at them during the scheduled pause in activities in Gaza.
The three-hour truce is scheduled to take place every other day, Lerner said, but humanitarian agencies say the timeframe is not long enough to alleviate the "deepening humanitarian crisis" in Gaza.
"We are feeding 750,000 [people] on a permanent basis," U.N. Relief and Works Agency spokesman Chris Gunness said. "We need to build on this three-hour window; we need to expand that window and let it lead to a permanent cease-fire."
The Israeli air force bombed targets in Rafah, Gaza, on Wednesday shortly after warning residents of the town to leave, the Israel Defense Forces confirmed. There were no immediate reports of deaths or injuries from the bombing, which threw up huge plumes of black smoke, visible even in the dark.
Israel has said Hamas, the Palestinian movement which controls Gaza, smuggles weapons from Egypt into Rafah on the Gaza side through underground tunnels. Shutting down that supply route is one goal of Israel's nearly two-week military operation against Hamas.
Israel said it "welcomes" a truce plan by Egypt and France and will continue its discussions with both countries about how to achieve a cease-fire in Gaza, an Israeli government spokesman told CNN.
Israel will send two envoys to Cairo, Egypt, in the coming days to discuss a Gaza truce plan, an Israeli foreign ministry official said Wednesday.
The envoys -- Defense Ministry official Amos Gilad and Shalom Turgeman, a political adviser to Israeli Prime Minister Ehud Olmert -- could head to Cairo as early as Thursday, the official said.
It is not clear whether Hamas, the Palestinian movement that governs Gaza, will send representatives to Cairo. Israel refuses to speak directly to Hamas, which it considers a terrorist organization, but it has negotiated with Hamas through Egypt in the past.
By Wednesday evening, 16 rockets had struck the Jewish state, according to the Israeli military. There was no immediate report of injuries.
At least 680 Palestinians have been killed and 3,000 wounded in Gaza since the campaign began on December 27, Palestinian medical officials said. Watch the aftermath of a rocket attack »
Nearly a third of the deaths and 45 percent of the injuries are women and children, according to the U.N.'s Office for the Coordination of Humanitarian Affairs. Seven Israeli soldiers and three civilians have been killed.
Tuesday was the bloodiest day of the Israeli ground offensive to date, when Israeli shelling struck a U.N. school in northern Gaza being used as a shelter by hundreds of civilians.
The Israeli military said Hamas militants were firing mortars from the school, prompting an artillery strike that killed at least 40 people and wounded dozens more. U.N. officials said there were no militants at the school.
"We are 99.9 percent certain that there were no militants. There were no militant activities in the school or in the school compound," said Gunness of the U.N. Relief and Works Agency.
The Palestine Red Crescent said five ambulances had been hit by Israeli forces, killing six people. The agency did not give a breakdown of paramedics and patients, and CNN was not able to independently verify these allegations. Learn what's behind the conflict »
The Israeli military said it was unaware of any such incidents.
Name: Zainuddin H.Abdulkadir Home: Pontianak, Kalimantan Barat, Indonesia About Me: Nothing ever happened in the past; it happened in the now, nothing will ever happen in the future;it will happen in the now. See my complete profile