The United States urged Israel on Thursday to do more to protect civilians caught in the crossfire between the Jewish state and Hamas, after Israeli air strikes killed four children in Gaza.

"We ask (Israel) to redouble their efforts moving forward to prevent civilian casualties, given the events of the last couple of days," State Department spokeswoman Jen Psaki told reporters.

"We believe that certainly there is more that can be done."

Psaki called images of the children's deaths "horrifying" and said that Secretary of State John Kerry has raised concerns directly with Israel.

"The tragic event makes clear that Israel must take every possible step to meet its standards for protecting civilians from being killed," Psaki said.

Footage of Wednesday's killings of four Palestinian children on a beach in Gaza by an Israeli strike was broadcast around the world.

Officials said that four more children were killed on Thursday, including at least three from the same family between ages seven and 10 in a Gaza City house.

Psaki reiterated that the United States has "strong concern" about Hamas and urged the militant group to stop firing rockets into Israel, the trigger for the military action.

New Gaza violence kills 4 children, hikes toll to 237
Gaza City, Palestinian Territories (AFP) July 17, 2014 - Israeli air strikes in Gaza killed four children on Thursday, medics said, after a humanitarian lull in a 10-day conflict that has killed 237 Palestinians.

One strike hit the Sabra neighbourhood of central Gaza, killing three children -- Jihad, Waseem and Fulla -- from the Shuheiber family, emergency services spokesman Ashraf al-Qudra told AFP.

Their deaths were the first to follow the end of a five-hour humanitarian ceasefire, which brought some respite for residents of the besieged Palestinian territory.

Another strike shortly afterwards in the southern city of Khan Yunis killed four-year-old girl Rahaf al-Jubur, and a 29-year-old man, Hamza al-Abadleh.

Before the ceasefire took effect at 10:00 (0700 GMT), Israeli tank fire killed three men in their twenties in the southern city of Rafah, Qudra said.

One Israeli has also been killed by rockets fired by Palestinian militants.

The Rafah deaths came after another seven Palestinians were killed overnight.

Two men were killed in Gaza City, another two in Deir al-Balah and a fifth in northern Beit Lahiya.

One man was also killed in southern Khan Yunis and another in Rafah, Qudra said.

In addition, 1,690 people had been injured during the conflict, Qudra said.

Israel and the Hamas movement announced Thursday they were observing a five-hour humanitarian truce requested by the United Nations.

According to figures provided by the Gaza-based Palestinian Centre for Human Rights (PCHR), more than 80 percent of those killed have been civilians.

The only Israeli fatality has been a civilian killed on Tuesday evening when a projectile exploded near the Erez crossing between Gaza and southern Israel, medics said.

At least four Israelis have been seriously wounded.

Since the latest violence began before dawn on July 8, at least 1,048 rockets fired from Gaza have struck Israel, and another 282 have been shot down by the Iron Dome air defence system, army figures show.

In its air war aimed at halting the rocket fire, Israel has struck more than 1,750 "terror targets" across the coastal enclave, the army said.