Israeli airstrikes have killed over two dozen Palestinians, making it the deadliest day since violence between the two countries began. World leaders are visiting the region to discuss a ceasefire to the conflict.
Sunday's violence was the worst yet in the five-day conflict, bringing the death toll to 72 Palestinians and three Israelis.
An airstrike targeting a top militant destroyed a three-story house, killing 11 civilians, four of whom were children, medical officials said.
Hamas' senior commander of rocket operations in Gaza Yihia Abayah had been the target, according to Israel's Chief Military Spokesman Yoav Mordechai.
Mordechai said he did not know if Abayah was killed, "but the outcome was that there were civilian casualties."
Gaza health officials say 21 children have now been killed in the occupied territory. In Sunday's strikes, 10 children were killed, including five babies and toddlers, while hundreds more have been injured.
In Israel, a further 50 people have been injured by rocket strikes from Gaza, according to medical sources. Israel has said its casualty numbers are low because only a fraction of the rockets from Gaza have hit populated areas.
On Sunday, French Foreign Minister Laurent Fabius met with Israeli officials and Palestinian Authority President Mahmoud Abbas.
"It's absolutely necessary that we move urgently towards a ceasefire, and that's where France can be useful," Fabius told French television.
"War is not an option - it is never an option," he said. "There are two key words: urgency and ceasefire."
The Palestinian Authority asked for an urgent Arab League conference to discuss Israeli attacks on Gaza. Abbas had previously been accused of not reacting strongly enough to the airstrikes on Gaza.
German Foreign Minister Guido Westerwelle is considering traveling to the region in the near future, according to a ministry spokeswoman.
United Nations General Secretary Ban ki-Moon is to visit Cairo Monday to talk with Egyptian President Mohamed Morsi. Egypt has been mediating talks with senior Hamas officials and Israel to end the violence.
"I strongly urge the parties to cooperate with all efforts led by Egypt to reach an immediate ceasefire," Ban said Sunday.
dr/mr (AFP, Reuters, dpa)