Israel and militants in the Gaza Strip have stepped up their attacks on each other, in some of the most intense exchanges of recent years.
The army says Palestinian militants have fired 600 rockets into Israeli territory over the weekend. Many were intercepted but three Israelis died.
Israel says it has hit 260 targets in the Gaza Strip and threatened further “massive” strikes.
Gaza officials say nine Palestinians have been killed since Friday.
On Sunday, Israeli Prime Minister Benjamin Netanyahu said he had ordered the military to “continue its massive strikes on terror elements in the Gaza Strip”.
Israeli forces around Gaza would be “stepped up with tank, artillery and infantry forces”, he added.
The flare-up comes despite a truce agreed last month. Egypt and the United Nations have recently been trying to broker a longer-term ceasefire.
How did the latest round of violence develop?
It began on Friday, during protests in Gaza against the blockade of the area – which Israel says is needed to stop weapons reaching militants.
A Palestinian gunman shot and wounded two Israeli soldiers at the boundary fence. Israel retaliated with an air strike that killed two militants.
The rocket barrage from Gaza began on Saturday morning. Israel’s Iron Dome missile defence system shot down dozens of the rockets, but a number of homes in Israeli towns and villages were hit.
What do we know about casualties?
Barzilai Hospital in Ashkelon, 10km (six miles) north of Gaza, has said it has treated more than 100 civilians in the last 24 hours.
Out of those, three people died and three more were seriously wounded – including an elderly Israeli woman.
Those killed were a 58-year-old man struck in a garden and two others at a factory, Israeli media say.
Israel air strikes targeted sites belonging to the militant groups Hamas and Islamic Jihad on Saturday and Sunday.
Hamas, which controls Gaza, has said the Palestinian dead include a woman and her 14-month-old daughter.
But Israel says the mother and baby may have been killed by a Palestinian rocket that fell short of its target.
On Sunday, the Israeli military said they had killed a Hamas commander named Hamed Hamdan al-Khodari in one of their strikes.
The sites destroyed include a multi-storey building in Gaza City, which Israel said included Hamas intelligence offices.
Turkey said its state news agency Anadolu had an office there. Foreign Minister Mevlut Cavusoglu called Israeli strikes on civilians “a crime against humanity”.
What about previous flare-ups?
It is the first deadly rocket attack from Gaza since the conflict of July and August 2014.
In that year, Israel launched a ground offensive on Gaza following the kidnapping and killing of three Israeli teenagers.
The conflict resulted in the death of 67 Israeli soldiers. Hamas and its allies launched more than 4,500 rocket strikes that killed six civilians in Israel.
On the Palestinian side, 2,251 people, including 1,462 civilians, were killed in the seven-week conflict, according to the UN.
Since then, Palestinian militants have continued to carry out sporadic strikes on Israel.
In a previous wave this year, in March, several rockets were fired into southern Israel, triggering raids on Gaza by the Israeli air force. No fatalities were reported on either side.
In early April a ceasefire was brokered by Egypt, but Hamas and allied militant groups later accused Israel of violating its terms.