Israel launched a series of air strikes on Gaza early on Monday to quell Hamas rocket fire, and the Islamist group's armed wing said seven of its gunmen were killed, making it the deadliest day for Hamas since a 2012 cross-border war with the Jewish state.
Israeli military authorities confirmed the strikes, saying they "responded to rocket attacks against southern Israel," targeting 9 "terror" sites and concealed rocket launchers. They said the attacks had made "direct hits".
Hamas said most of the strikes were launched at a gathering point for its members in Gaza's southern-most town of Rafah, at the Egyptian border. Another strike was launched in northern Gaza, it said.
Seven Hamas fighters were killed and four people were wounded in the attacks, the group's armed wing said in a statement.
The attacks followed a surge in rocket strikes at Israel from Gaza, where Hamas is the dominant force. The Israeli military said these attacks have topped 150 since mid-June, including 25 rockets striking Israel on Sunday.
Prime Minister Benjamin Netanyahu pledged to his cabinet on Sunday "to do whatever is necessary" to restore quiet to southern Israeli communities.
Netanyahu also cautioned against any rush toward wider confrontation with Hamas, whose arsenal includes long-range rockets that can reach Israel's heartland and its business capital, Tel Aviv.
But far-right members of Netanyahu's cabinet and politicians in Israel's south have pushed for a stronger response to the rocket fire that has disrupted life for many Israelis living in the region where air raid sirens send them running for shelter.
Hamas spokeman Sami Abu Zuhri accused Israel of committing a "grave escalation" in violence and threatened to retaliate, saying Israel would "pay the price."
Tensions between Israelis and Palestinians have also risen over the burning alive of 16-year-old Mohammed Abu Khudair of East Jerusalem a week ago, a killing that has sparked protests across Israel's normally quiet Arab towns as well.
Israel has arrested six Jewish suspects in the teenager's kidnapping and slaying.
Police have cited a gag order barring publication of details about the suspects, but Israeli media have said they include minors and that they come from the Jerusalem area and a nearby Jewish settlement.
Israel also blamed the kidnap and slayings of three Israeli teens last month on Hamas. Their bodies were found last week near the West Bank city of Hebron, a Hamas stronghold.
Monday's fatalities were the single largest toll for Hamas since Israel's "Pillar of Defence" campaign in late 2012 launched to halt rocket fire at its towns. In that eight-day war, some 180 Palestinians and six Israelis were killed.