All four were on the beach on Wednesday when the attack took place, in what initially appeared to be shelling from the sea, according to AFP correspondents who witnessed the attack from a nearby hotel.

Several injured children took refuge at the hotel, they added.

The latest violence took Wednesday's death toll to 16, and raised the overall number of dead in Gaza after nine days of violence to 216, emergency services spokesman Ashraf al-Qudra said. More than 1,560 have been wounded.

Earlier, a 37-year-old man was killed in an air strike on the Zeitun neighborhood, east of Gaza City, which took place several hours after the army warned 100,000 residents to leave the area and the neighboring district of Shujaiya.

Most of Wednesday's deaths came in the south, with six killed in several strikes on Khan Yunis and five killed in Rafah, which straddles the Egyptian border.

In Khan Yunis, four people from the al-Daqqa family were killed in two separate strikes, one of which killed a 65-year-old woman and a 10-year-old boy.

One of the victims in Khan Yunis was killed by tank fire.

In Rafah, five men were killed in four separate strikes, one of which hit a house in the city, Qudra said.

According to figures provided by the Gaza-based Palestinian Center for Human Rights (PCHR), more than 80 percent of the victims were civilians.

So far, one person has been killed in Israel -- a man who died on Tuesday evening in a rocket strike near the Erez crossing, medics said. Four Israelis have been seriously wounded.

Since the latest violence began before dawn on July 8, 1,021 rockets fired from Gaza have struck Israel, and another 256 have been shot down by the Iron Dome air defense system, army figures show.

Forty-three struck Israel on Wednesday and 24 were intercepted.

During its attacks, Israel has struck more than 1,750 targets across the coastal enclave, the army said.

HH/HH