Israel hit the Gaza Strip with missiles and artillery for the first time in three days, while Palestinian fighters launched a barrage of rockets at Israel, just hours after a ceasefire between the two sides expired.

Five Palestinians were killed and at least 31 others wounded in Friday's air strikes, said Ashraf al-Qudra, Gaza's health ministry spokesman. Among the dead was a 10-year-old boy.

The Israeli army said that as of Friday afternoon, more than 45 rockets were fired into southern Israel after the truce ended. Three of the rockets were intercepted by the Iron Dome missile defence system. Two Israelis were wounded, the army said.

"Following renewed rocket launching at Israel, the IDF [Israel Defence Forces] targeted terror sites across the Gaza Strip," a statement from the military read.

Thousands of Palestinians fled their homes east of Gaza City amid the renewed Israeli attacks, witnesses reported.

At least one teenager was also killed in the West Bank. More than 2,500 people demonstrated in the Palestinian territory on Friday against the Gaza operation, Al Jazeera's Dalia Hatuqa, reporting from Ramallah, said.

The ceasefire expired as no progress was made in the Egyptian-mediated talks aimed at finding a durable solution to the month-long fighting.

Talks among the main Palestinian factions in Cairo were still ongoing on Friday.

"They are discussing with the Egyptians the demands that haven't been met and the sticking points in the negotiations," Al Jazeera's Nisreen El-Shamayleh, reporting from West Jerusalem, said.

She added that Israel had pulled out of the talks early on Friday, before the ceasefire expired.

Among the top demands are the lifting of the blockade in Gaza and the opening of the Gaza port.

Earlier this week, Israel had said it was ready to "indefinitely" extend the ceasefire.

"We understand from senior Israeli officials that Israel would not continue the negotiations while it is coming under fire, and that these negotiations would remain frozen as long as Hamas and other Palestinian factions are firing rockets," our correspondent said.

"It seems that the Israelis, for now, are boycotting the talks," she said.

'Deeply distressed'

The Palestinian side is also demanding the release of around 125 key prisoners held in Israeli jails.

Despite the withdrawal of all its troops from Gaza by the time the three-day truce began early on Tuesday, Israel has retained forces along the border, ready to respond to any resumption of fighting.

Four weeks of military assault on Gaza has claimed the lives of at least 1,893 Palestinians, according to Gaza officials. UN figures indicate that 73 percent of the Palestinian victims were civilians. Of that number, at least 429 were children.

On the Israeli side, three civilians were killed by rockets fired from Gaza while at least 64 soldiers died in the fighting.

Ayman Taha, a former spokesman for Hamas - the son of one of the group's founders - was found dead on Thursday in a neighbourhood of Gaza City that was heavily bombed by Israel, the movement said.

Speaking in Jerusalem after a visit to Gaza, International Committee of the Red Cross president Peter Maurer said he was "deeply distressed and shocked" at the impact of violence, saying the scale of the civilian losses must not happen again.

He also suggested there may have been violations of international humanitarian law.