The latest round of Israeli airstrikes on Gaza and the West bank came after a day of heavy artillery shelling and rocket fire on Israel, the US, Jordan and Egypt.
At least three people were killed in Gaza.
In the West, the Palestinian Authority (PA) claimed that Israeli forces had opened fire on a family of four in the Gaza Strip, killing their two daughters and three-year-old son.
It accused Israel of attacking a mosque in Gaza City that had been under security lockdown and then attacking it with missiles.
Israel responded with a barrage of artillery fire on Gaza City, killing two Palestinians and wounding 15.
Hamas accused Israel, Egypt and the United States of “sticking the boots to the Palestinian people” and “killing our children”.
The US, which was to hold its annual meeting in Jerusalem on Wednesday, also blamed Israel for the latest round.
“We have been monitoring the situation on the ground and know that the attacks have not been carried out by the Israeli side,” US State Department spokesperson Jen Psaki told reporters.
“What is clear is that the Israeli regime has escalated the conflict by attacking innocent civilians in Gaza.”
A Palestinian man walks near a damaged house following an Israeli air strike on Gaza, in the West Daraa Governorate, north of the capital, on Sunday.
The UN says the Israeli military is targeting hospitals and ambulances and targeting the UN Relief and Works Agency for Palestine Refugees in the Near East (UNRWA), which operates schools in Gaza and West Bank refugee camps.
In a statement on Sunday, the PA condemned “the attack on hospitals and other civilian infrastructure in the besieged areas of Gaza, which is a flagrant violation of international law”.
Israel, meanwhile, fired more than a dozen rockets into the Israeli-occupied Gaza Strip.
According to the Israeli army, at least 18 rockets fired from Gaza hit the southern Israeli city of Ashkelon.
Israeli officials said on Sunday that the rockets were fired from the Gaza border region, which they said was targeted at Israeli civilians.
Earlier, on Saturday, Israel launched an air strike against a Hamas-run military building in the northern Gaza Strip which was believed to have been used as a weapons storage area.
It also targeted a military facility in Gaza’s northern city of Khan Younis.
Israeli Prime Minister Benjamin Netanyahu also blamed Hamas for the “massive escalation” in the conflict, adding that it was the result of its refusal to accept the UN “just peace” plan.
He also said that Israel was ready to deal with “all those who try to turn Gaza into a military objective” and that Hamas was not acting in the interests of the Palestinian population.
“This is an act of aggression, a direct threat to our people and to our way of life,” Netanyahu said in a statement.
“Israel has a responsibility to defend ourselves and to defend the innocent people of Gaza.”
The Palestinian leadership has accused Israel and Hamas of a series of ceasefire violations and a violation of the truce, which it brokered in 2013, in which Israel allowed Palestinians to enter Gaza to carry out medical treatment, food distribution and medical aid.
Israel has maintained that it will not recognize a Palestinian state if the two sides do not agree to a peace deal.
The latest flare-up came after Israel and Egypt agreed to suspend hostilities in exchange for an end to the blockade of Gaza and an end of the blockade imposed by Egypt on Gaza.
On Sunday, Netanyahu announced that he was sending a letter to Egyptian President Abdel Fattah al-Sisi asking for an extension of the Gaza ceasefire.
Egypt said on Saturday that it had agreed to resume the truce in the face of “unprecedented aggression”.
“Egypt has decided to resume a cessation of hostilities with Israel, a decision which we are happy to make, since it is in our interest,” a senior Egyptian official told AFP news agency.
“In this way, the ceasefire is going to be extended.”
Israeli PM Netanyahu speaks to Israeli troops in the occupied West Bank city of Hebron on Saturday.
Netanyahu, who has previously accused the PA of “disguising its Palestinian origins”, also said on Friday that he would be willing to meet with the new Palestinian president of Israel, Mahmud Abbas, in order to discuss the future of the Israeli occupation.
“The Palestinian people has the right to choose a president who will be a friend of the people of Israel and who will also lead the Jewish state in the Middle East,” Netanyahu told a press conference.
“I will meet with him at the right time, when the Palestinian leadership will be able to make decisions.”
“The Israeli people knows that if we don’t have a president with whom we can talk about the future, the Israeli people will not accept it.”