Israeli aircraft have killed three top Hamas commanders in southern Gaza, inflicting a heavy blow on the movement's armed wing after failing to kill its top military chief.
Thursday's attack, on a day when a total of 26 people were reported killed in Gaza, came a day after the Israeli prime minister, Benjamin Netanyahu, said Israel's offensive may be an extended operation.
The Qassam Brigades, Hamas's military wing, said Mohamed Abo Shamaleh, Raed al-Attar and Mohamed Barhoum had been killed in an Israeli attack in Rafah, the Reuters news agency reported.
The raid came a day after Israel attempted to kill the brigades' leader Mohammed Deif. Dief's wife and baby son died in the attack.
"The assassination... is a big Israeli crime, which will not succeed in breaking our will or weakening our resistance," said spokesman Sami Abu Zuhri, adding: "Israel will pay the price."
Al Jazeera's Jacky Rowland, reporting from West Jerusalem, said Israel had turned to its historical tactic of targeting senior figures.
"This could be seen as an acknowledgement that military tactics have not been delivering on several different levels," she said.
Israel said on Thursday it was rotating 10,000 troops - meaning fresh soldiers were being prepared for future operations.
At a news conference on Wednesday in Tel Aviv, Netanyahu pledged "a continued campaign" in Gaza aimed at restoring "calm and safety to Israeli citizens".
"Operation Protective Edge is not finished, not for a minute, we are talking about a continued campaign," Netanyahu said, before adding he saw a "new diplomatic horizon for the state Israel" in the coming months.
Hamas spokesman Zuhri denounced Netanyahu's speech as "a pathetic attempt to heal Israel's psyche".
"The assassination threats ... reflects the extent of the occupation's violence and [Israel's] lack of seriousness in achieving a ceasefire," he said
"These threats will not frighten Hamas leaders. We will continue to protect and defend our people in facing Israeli crimes or foolishness," he said.
Al Jazeera's Jane Ferguson, reporting from Gaza, said the Hamas commanders killed on Thursday had been implicated in the kidnapping of its soldier Gilad Shalit, who was freed in 2011 under a prisoner swap deal with Hamas.
She added that Hamas and other Palestinian factions were still open to talks, an "indicator of how both sides ... are aware that while they say they're prepared to fight, they also know that they need a political solution at some stage".
Hamas is seeking an end to a seven-year Israeli-Egyptian blockade that has battered Gaza's economy, while Israel wants guarantees that Hamas will disarm.
More than 40 Palestinians have been killed by Israeli air strikes in Gaza since a week-long ceasefire collapsed on Tuesday, raising the total death toll to over 2,035 since the beginning of Israel's "Operation Protective Edge" on July 8.