GAZA/JERUSALEM (Reuters) - Palestinian militant group Islamic Jihad offered terms on Wednesday for an Egyptian-mediated ceasefire with Israel, saying if these were not met it was prepared to keep up cross-border rocket salvoes indefinitely despite a mounting Gaza death toll.

The worst surge in fighting around the Palestinian enclave was sparked on Tuesday when Israel killed Islamic Jihad’s top Gaza field commander in an air strike, accusing him of masterminding a spree of recent attacks and planning more soon.

As Islamic Jihad fighters responded with hundreds of rocket launches that reached as far as Tel Aviv and paralyzed parts of Israel, it pressed the aerial barrage on the Gaza Strip.

Medics say 26 Palestinians, including at least 14 gunmen and six civilians, have been killed. Dozens have been injured on both sides.

In his first public comments on the fighting, Islamic Jihad leader Zeyad al-Nakhala said a truce could be agreed immediately if Israel accepted the Iranian-backed faction’s terms.

These included Israel ending targeted killings of militants, its sometimes lethal response to weekly Gaza protests and steps to ease its blockade on the coastal Palestinian enclave, al-Nakhala, who is based in Beirut, told Al-Mayadeen TV.

Al-Nakhala said he expected to hear Israel’s response via Cairo within hours. Should a truce not be agreed, he said, “the (Islamic Jihad armed wing) Jerusalem Brigades is able to manage the battle, and for a long time”.

Israel signaled openness only to a quid-pro-quo restraint.

“Quiet will be answered with quiet,” Israel’s Army Radio quoted an unnamed Israeli government official as saying. “Islamic Jihad wants a ceasefire, and it is thus trying to create a false impression of achievements.”

Israel had previously said it sought no escalation in Gaza. Unlike with past rounds of fighting, when Israel held Gaza’s dominant Hamas faction responsible for any cross-border attacks, this time Hamas has been spared Israeli retaliation.

Hamas, in turn, has voiced solidarity with Islamic Jihad but has not claimed responsibility for any of the rocket launches.

CIVILIANS SUFFER

The Israeli military said it had “eliminated” at least 20 Gaza fighters since Tuesday in attacks on targets that included a rocket warhead manufacturing facility, an Islamic Jihad headquarters and a weapons storage site. Islamic Jihad confirmed that several of its militants were killed in separate strikes.

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In the north of Gaza City, family members said Rafat Ayyad and his two sons Islam, 25, and Ameer, aged 9, were killed by Israeli fire while rushing to hospital to visit another son who had earlier been injured in a separate attack.

“I got wounded and I called my father. He was coming to see me in hospital and two of my brothers were with him on the motorcycle when they were hit by Israel,” Loay Ayyad, 18, told Reuters during the funeral.

Despite their enmity, Hamas and Israel have managed to defuse previous confrontations and avoid a full-scale conflict for the past five years, following three wars from 2008-2014.

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U.N. Middle East peace envoy Nickolay Mladenov earlier on Wednesday condemned “the indiscriminate launching of rockets and mortars” at Israeli civilians as “absolutely unacceptable” and said it “must stop immediately”.

The salvoes from Gaza sent Israelis rushing to shelters in towns near the Gaza border and deeper in the country, with air raid sirens going off as far north as Tel Aviv and rockets striking Israeli highways and towns. Israel’s Iron Dome air defense system shot down dozens of rockets, the military said.

Israel assembled armored vehicles along the Gaza border. But a ground incursion seemed unlikely at this stage.

“We don’t want escalation, but we are responding to every attack against us with a very sharp attack and response. Islamic Jihad best understand that now rather than when it’s too late for it,” Israeli Prime Minister Benjamin Netanyahu said earlier.