Israel has carried out a series of air strikes on Gaza, targeting those it blamed for an attack on Thursday in which eight Israelis died.
At least 14 Palestinians are reported to have been killed since Thursday.
Meanwhile, Egypt on Friday formally complained to Israel over the deaths of five of its policemen who Cairo says were caught up in shooting a day earlier.
Israeli media said rockets had been fired at Ashkelon, Beersheva, Kiryat Gat and Ashdod on Friday morning.
Most landed in open ground, causing no damage or injuries, but one landed in the grounds of a religious seminary, or yeshiva, seriously wounding one person.
Another hit an industrial park on the outskirts of Ashdod, injuring six, Israel's Haaretz newspaper reported, while the rocket aimed at Ashkelon was shot down by Israel's new Iron Dome missile defence system.
Four members of the Popular Resistance Committees (PRC) - a group that is loyal to Hamas but sometimes operates separately - died in the Israeli strikes on Gaza throughout Friday, Haaretz said.
Palestinian medical officials said three members of the same family, including a five-year-old boy, died in one strike.
Israel carried out the raids in response to a series of attacks near Eilat on Thursday in which gunmen opened fire on several vehicles and detonated a bomb on one bus.
Series of attacks
- Shooting attack on bus near Eilat wounds 14 Israelis, including five soldiers
- Other vehicles hit soon after, killing eight Israelis - six civilians and two security personnel
- Israeli military patrol vehicle targeted, no immediate reports of injuries
- Seven suspected gunmen are killed as Israeli security forces confront them
- Israeli air strikes on Gaza kill at least seven people, including a militant leader and a child
- Several Israelis injured, one seriously, by rocket attacks on southern Israel
But Israeli Prime Minister Benjamin Netanyahu said the overnight air strikes had killed those responsible.
A spokesman for Israel's domestic security agency, Shin Bet, said several of those who died in the air strikes had been involved in the 2006 kidnapping of Israeli soldier Gilad Shalit.
Hamas said it would retaliate if Israel attacked.
The Hamas-run ministry of health in Gaza accused Israel of committing "war crimes".
On Friday, Egypt filed a formal complaint to Israel over the deaths of five of its policemen close to the border. Three were killed by gunfire on Thursday and two died of their wounds on Friday, said officials.
"Egypt has demanded an urgent probe into the circumstances of the deaths and injuries of Egyptian forces' members inside our borders," the Mena news agency quoted a military official as saying.
The US, the EU and the UN have all condemned the Eilat attacks, while a UN spokesman said Secretary-General Ban Ki-moon was "concerned at the risk of escalation and calls for all to act with restraint".
Israeli officials said the men who attacked the vehicles near Eilat came from the Gaza Strip and had entered Israel through Egypt's Sinai desert.
BBC Middle East editor Jeremy Bowen, in Jerusalem, says the desert region has become increasingly lawless since the Egyptian revolution that ousted President Hosni Mubarak, with a rise in al-Qaeda-inspired militant activity.
However, given the substantial distance between the Sinai desert and Gaza, it is unclear why Israel is so certain the attackers were Gazans, says our correspondent.