Israeli air strikes on the Gaza Strip killed 21 people Thursday, medics said, on the third day of a widening military campaign, as the UN Security Council was set for an emergency meeting.
The first strike hit a coffee shop in the city of Khan Yunis, emergency services spokesman Ashraf al-Qudra told AFP, adding that six men were killed and at least 15 other people wounded.
The second, in Nusseirat refugee camp in central Gaza, on the home of Raed Shalat, killed him and wounded several others, Qudra said.
Further strikes on two houses in Khan Yunis killed seven people - three women and four children, he said.
The deaths bring to 72 the overall number of Gazans killed since Israel launched Operation Protective Edge early on Tuesday to halt cross-border rocket fire.
Dozens of strikes were heard slamming into the besieged Palestinian territory in the early hours of Thursday, as Israel's Operation Protective Edge, the largest military campaign against Gaza since 2012, entered day three.
An army spokesman said Thursday that the Israeli air force overnight hit more than 300 Hamas targets in the Gaza Strip.
"We aimed at 322 targets in Gaza overnight, taking to 750 the total number of Hamas targets hit by the army since the start (on Tuesday) of Operation Protective Edge," Lieutenant Colonel Peter Lerner told journalists in a telephone conference.
Among the targets hit were rocket-launching sites of Hamas's armed wing the Ezzedine al-Qassam Brigades, as well as tunnels used by the group and Hamas command posts, Lerner said.
He warned that a ground assault was still being considered.
"More than 20,000 reservists have been recruited but a ground assault would be the last option if we judge it necessary," he said.
Israel's cabinet has authorised the call-up of 40,000 reservists for such an operation, which looks increasingly likely as the conflict drags on, commentators say.
On Wednesday, 30 Palestinians were killed, and Tuesday's toll stood at 21, bringing the total number of dead to 72. But Hamas kept up its rocket fire into Israel and sent thousands running to shelters across the country.
The dead include at least 10 women and 18 children, according to an AFP count based on medical reports.
The Israeli military said a rocket was intercepted over Tel Aviv on Thursday morning.
A spokesman earlier told AFP that two rockets had been intercepted by Israel's Iron Dome anti-missile system, but subsequently revised the number down.
In the Gaza Strip, where Israel has been carrying out a widespread aerial campaign, the armed wing of the Hamas movement announced it had fired two M75 rockets at Tel Aviv.
"The Qassam Brigades struck Tel Aviv with two M75 rockets," the Ezzedine Al-Qassam Brigades said in a statement.
The locally-produced M75 rocket has a range of about 80 kilometres (50 miles), able to reach Tel Aviv, which lies around 70 kilometres from the Gaza Strip.
Palestinian president Mahmud Abbas accused Israel of committing "genocide" in Gaza but Israeli Prime Minister Benjamin Netanyahu warned of even tougher action to come.
Tanks were seen massed on the Gaza border as Netanyahu came under mounting pressure from hardliners within his governing coalition to put boots back on the ground in the territory from which Israel pulled all troops and settlers in 2005.
President Shimon Peres warned that, "if the fire continues we do not rule out a ground incursion", his office quoted him as saying in an interview with CNN.
This "may happen quite soon", said Peres.
Israeli troops on Wednesday killed two Palestinians who came ashore on dunes close to the Gaza border, near the scene of a foiled assault on an army base the night before.
Troops killed four under almost identical circumstances on Tuesday.
The United Nations Security Council will hold an emergency meeting on the crisis from 10:00 am (1400 GMT), with UN Secretary-General Ban Ki-moon due to give the latest about the situation on the ground, followed by closed-door consultations between the Council's 15 member states.
The meeting follows a request by Arab envoys.
- Gaza is 'on a knife edge' -
Ban called the new wave of violence "one of the most critical tests the region has faced in recent years".
"Gaza is on a knife edge. The deteriorating situation is leading to a downward spiral which could quickly get beyond anyone's control," he said.
"The risk of violence expanding further still is real. Gaza, and the region as a whole, cannot afford another full-blown war."
Ban earlier spoke with world leaders including Netanyahu, Abbas and Egypt's President Abdel Fattah al-Sisi, as well as US Secretary of State John Kerry.
He condemned the rocket attacks, saying: "Such attacks are unacceptable and must stop."
He also urged Netanyahu to exercise maximum restraint and to respect international obligations to protect civilians.
The European Union and the United States also called for restraint.
In Jeddah, Saudi Arabia the executive committee of the Organisation of Islamic Cooperation was to discuss the spiralling crisis Thursday.
The escalation comes with Arab riots inside Israel over the burning to death of a Palestinian teenager by Jewish extremists.
The boy was murdered in apparent revenge for the kidnap on June 12 of three Israeli youths in the occupied West Bank, who were subsequently killed.
Their abductions sparked a huge Israeli assault on Hamas's infrastructure in the territory and retaliatory rocket fire from the Islamists' Gaza power base.
Three of the six Israelis held over the young Palestinian's abduction and killing last week are to be released on Thursday, Israeli media said, raising the spectre of renewed unrest by outraged Palestinians.
The three expected to be let out of custody deny involvement in the murder, while the remaining three are said by authorities to have confessed.