Palestinian officials say at least 23 Palestinians have been killed in two separate Israeli attacks in the West Bank and Gaza Strip.
At least 18 people died and dozens were wounded when Israeli fire struck houses near the northern Gaza town of Beit Hanoun early Wednesday morning.
Palestinian officials say the victims were civilians - many women and children - who were sleeping at the time of the attack.
Palestinian leaders are calling for urgent U.N. Security Council action to stop what they describe as Israel's "massacre of Palestinian people."
The Israeli army says the firing was in response to rocket attacks by militants.
In the West Bank, Israeli troops ambushed and killed four Palestinian militants near the town of Jenin. One civilian died during the firefight.
Palestinian officials identified the militants as members of the Al Aqsa Martyrs Brigades group, which is linked to Palestinian President Mahmoud Abbas' Fatah faction.
Fatah has been holding talks with the ruling militant group Hamas on forming a unity government with the hope that a new government will convince Western nations to resume aid to the Palestinian Authority.
But after Wednesday's Israeli shelling, Palestinian Prime Minister Ismail Haniyeh - a Hamas leader - called for the suspension of the talks.
Some information for this report was provided by AFP, AP and Reuters.