Israel claimed a significant blow against al-Qaida-inspired militants in the Gaza Strip Sunday, killing one of the most influential leaders from an extreme branch of Islam that has targeted Egypt and Gaza's Hamas rulers as well as Israel.

Hisham Saidani was killed alongside another top militant in the northern Gaza Strip in an airstrike late Saturday, Israel's military said. He was one of the main ideological guides for the violent, ultra-conservative Islamic movements in Gaza known as Salafi jihadis.

The Israeli military said Saidani, 43, was suspected of carrying out attacks against Egyptian and Israeli targets, but they would not provide further information.

Militants on jihadi websites identified the other dead man as Ashraf Sabah, 37. They said he was the leader of another al-Qaida inspired group, Ansar al-Sunnah.

In recent years, a number of shadowy groups that claim inspiration from al-Qaida have been on the rise in Gaza. While they are not believed to have direct links with the global terror network, they share the same belief that they can impose their fundamentalist version of Islam by force and frequently borrow its tactics. They have also clashed with Gaza's ruling Islamic militant Hamas movement.

Saidani led a small group, "Tawhid wal Jihad," or "Monotheism and Holy War," believed responsible for killing of an Israeli civilian working along the Egyptian border last June. He was also linked to the Mujahideen Shura Council, another militant group operating in Gaza and Egypt's neighboring Sinai desert.

Salafi militants first emerged in Gaza around 2005, after Israel withdrew from the territory. Members of one such group, the Army of Islam, cooperated with Hamas in the abduction of an Israeli soldier the following year. But after Hamas seized power in Gaza in 2007, differences emerged, and the sides parted ways.

Several hundred Salafi militants are now believed to be in Gaza. Saidani was the best known.

Saidani returned to Gaza in 2008 when Gaza militants blew a hole through the border fence with Egypt. Thousands of people crossed the border at the time.

Followers of Saidani were responsible for kidnapping and killing Italian activist Vittorio Arrigoni in Gaza in March 2011. Saidani later denounced the act.

He sought to unite the many groups of ultraconservative Salafis in Gaza, according to jihadis commenting about his death.

In response to Saidani's death, al-Qaida's media arm warned Israel that its "joy will not last long."

"We fully trust our brothers that they will be capable of avenging the killing," said a statement by the Global Islamic Media Front, a European group that supports al-Qaida and other extremist organizations. The statement underscored Saidani's prominence among jihadis.

Over the past year, Israel has targeted militant Salafi militants with airstrikes in Gaza, seeing them as a new threat to its southern border.

On Sunday, Israeli airstrikes killed three more militants, said Palestinian health spokesman Ashraf al-Kidra. In all, five militants were killed in weekend fighting.

Israeli officials believe the militant Salafis sometimes cross between Gaza and Sinai, using the lawless Egyptian territory as a base to conduct attacks, or to flee after carrying out attacks elsewhere. Many adopt a Pakistani style of dress: long loose shirts over baggy pants, sandals and turbans.

They are considered a threat not only to Israel, but to Hamas and Egypt as well.

Militant Salafis consider Hamas, which itself is dedicated to Israel's destruction, to be too moderate because it seeks to establish a Palestinian state. Instead, they believe all Muslim lands should be united under the rule of fundamentalists, forcefully applying an extremely conservative version of Islam.

Most Salafis disavow militancy. They have lived quietly in Gaza for decades, some in separate, closed communities.

Hamas arrested Saidani, also known as Sheik Abu Walid-al-Maqdasi, last year in the one of most high-profile arrests against the territory's militant Salafis. He was released two months ago.

Saidani was also imprisoned in Egypt after he tried to join militants fighting in Iraq. He was arrested again after he tried to enter Gaza through smuggling tunnels that connect the two territories, according to a militant website that listed Saidani's biography.

Speaking to his Cabinet on Sunday, Israeli Prime Minister Benjamin Netanyahu praised the attack.

"The global jihad is stepping up its efforts to harm us, and we will continue to act against it aggressively and powerfully, both reactively and pre-emptively," Netanyahu said.

During the last few days of violence, Palestinians fired more than 40 rockets at Israeli communities near Gaza, the military said. The salvos damaged property, but nobody was hurt.

Israel says it holds Hamas responsible for the barrages because it rules Gaza. The two have largely maintained an unwritten truce since a brief war nearly four years ago, but flare-ups occur occasionally.

In a separate development, the U.N.'s Middle East envoy harshly criticized attacks blamed on Israeli settlers against Palestinian farmers and their olive trees in the West Bank.

In a statement, Robert Serry said Israel must do more to protect Palestinians and their property in the West Bank. The West Bank, claimed by the Palestinians for a state, is under Israeli military rule.

"These acts are reprehensible, and I call on the government of Israel to bring those responsible to justice," Serry said.

The Israeli military said security forces were taking "every measure to ensure the safety and security of the local residents."


Additional reporting by Maamoun Youssef in Cairo and Diaa Hadid in Jerusalem. Follow Hadid on twitter.com/diaahadid