The deaths bring to 70 the number of Palestinians killed since Israel on Tuesday launched Operation Protective Edge to halt rocket fire from the besieged territory.
Israel's army said it carried out raids during the night against more than 300 Hamas targets, claiming to have hit the militant group a total of 750 times since the operation began.
Emergency services spokesperson Ashraf al Qudra told AFP that an early morning strike hit a coffee shop in the city of Khan Yunis, killing eight people and wounding at least 15.
A second attack blasted a home in Nusseirat refugee camp in central Gaza, killing one person and wounding several others, Qudra said.
Further strikes targeted two houses in Khan Yunis, killing four women and four children, he said.
After dawn, a car was hit in western Gaza City, killing three people and wounding four others.
Throughout the night explosions were heard across the Palestinian territory after Israeli Prime Minister Benjamin Netanyahu warned of even tougher action to come.
The military operation is Israel's largest against Gaza since 2012.
On Wednesday, 29 Palestinians were killed, and Tuesday's toll stood at 21, bringing the total number of dead to 70.
The dead include at least 11 women and 18 children, according to an AFP count based on medical reports.
There have been no Israeli deaths so far, but Hamas showed its firepower as it launched waves of rockets across Israel that triggered sirens in cities as far from Gaza as Tel Aviv, Jerusalem, and Haifa.
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@Zaid Hamid: So to retaliate it means killing 70+ plus women and children, to retaliate it means fire bombs directly into civilians, to retaliate it means killing little child's. Shame on you for supporting the brutality!!
It all started with kidnapping and killings of three Israeli teenagers by Hamas.
@p r sharma: Constraint will allow then to regroup and attack again.
@Hafsa Hashmey: Islamic states didn't do anything when brutality was happening in Afghanistan.
@Arshad: Baring few none of the Islamic state or Muslims themselves believe in human rights. Pakistan itself was created on that basis.
@Hafsa Hashmey: Israel bombing started to HALT the rockets launched by Hamas. The bombing is seen as a retaliatory action . Palestinian Hamas does not stand anywhere against the Israeli army and they have to bear the brunt on misadventure. These are the hard facts But i feel ( wish) that Israel could have used some constraints to avoid casualties of women and children. There is no concept of Ummah and the same is visible in the ongoing crisis in Middle east where Muslims are fighting/ killing Muslims.
When Hamas fires rocket in Israel, they are mard-e-mujahid, brave and fighting jews but when Israel retaliates then Israel is terrorist state, killing innocents bla bla bla.... #Yakin_Janiye.
@Good Job: Shame on your Indian supporting murder of innocents.
It could have been 200 if Israel had used cluster bomb .
@Hafsa Hashmey: You can see by the number of comments that how much the Muslims care about the brothers. Everyone is talking about Brazils loss in the quarter final.
The world as we see today doesn't seem to have changed much. Those advocates of 'civilization, prosperity, development and human rights" are no where to be seen.
So many innocent people being massacred and not one single Islamic state is doing anything to intervene and stop this brutality. The rest of the world is too busy with the FIFA world cup.