WASHINGTON - The White House on Friday urged Israel and the Palestinians to resume talks and do what they can to protect civilians after Egyptian-mediated negotiations failed to extend a ceasefire and rocket fire resumed.
Meanwhile, United Nations Secretary-General Ban Ki-moon condemned the renewed rocket fire on Israel and also called for a return to a truce in Gaza.
"The United States is very concerned about today's developments in Gaza," White House spokesman Josh Earnest told reporters.
"We condemn the renewed rocket fire and we are concerned about the safety and security of civilians on both sides of that conflict," he said.
The secretary general expressed his "deep disappointment" over the failure to extend the 72-hour truce that expired Friday and said peace talks in Cairo should continue.
Ban "condemns the renewed rocket fire towards Israel. More suffering and death of civilians caught up in this conflict is intolerable," said a statement from his spokesman.
"The extension of the ceasefire is absolutely essential for talks to progress."
Ban "firmly" called on the Palestinians and Israel "not to resort to further military action that can only exacerbate the already appalling humanitarian in Gaza."
The violence ended the three-day lull in fighting between Israel and Hamas that, since July 8, has killed at least 1,898 Palestinians and 67 people on the Israeli side.
Israel launched air strikes across the Gaza Strip on Friday in response to Palestinian rockets after Egyptian-mediated talks failed to extend a 72-hour truce in a month-long war.
Egypt later called for a resumption of the ceasefire, saying only a few points remained to be agreed. Palestinian factions said they would meet Egyptian mediators later in the day but there was no sign of any imminent deal.
An Israeli official said Israel would not negotiate with Palestinians while militants continued to unleash missiles.
As warning sirens sounded in southern Israel, the military said "Gaza terrorists" had fired more than 55 rockets on Friday morning and the "Iron Dome" interceptor system had brought down two.
Islamic Jihad and the Popular Resistance Committees claimed responsibility for the salvoes from the Hamas-dominated enclave.
Accusing Hamas of breaking the ceasefire, Israel said several of the rockets had been launched about four hours before the truce was due to end at 8 am (0500 GMT). Heavier barrages followed shortly after the ceasefire period expired.
By resuming the attacks, Gaza militants appeared to be trying to put pressure on Israel, making clear they were ready to fight on to end a blockade of the coastal territory that both Israel and neighboring Egypt have imposed.
Reuters and AFP contributed to this report