GAZA/JERUSALEM (Reuters) - Palestinian militants on Monday carried out their most intensive shelling of Israel since the 2014 Gaza war in retaliation for a botched cross-border commando raid, drawing Israeli air strikes against Hamas’ television station and other targets.

The flare-up, in which three Palestinian gunmen and a civilian in Israel were killed, threatened to derail efforts by the United Nations, Egypt and Qatar to broker a long-term truce and head off another major conflict in the impoverished enclave.

Hamas, Gaza’s dominant Islamist movement, and other armed factions launched more than 300 rockets or mortar bombs across the border after carrying out a surprise guided-missile attack on a bus that wounded an Israeli soldier, the military said.

Sirens in southern Israeli towns and the port of Ashkelon sent residents rushing to bomb shelters. Several homes were hit.

Israel responded with dozens of air strikes against Gaza buildings including a Hamas intelligence compound and the Al-Aqsa Television studios, whose employees had received advance warnings from the military to evacuate.

Egypt urged Israel to back down. The United States, whose peace mediation has been stalled since 2014, condemned Hamas.

“The escalation in the past 24 hours is EXTREMELY dangerous and reckless,” tweeted Nickolay Mladenov, a U.N. Middle East envoy. “Rockets must STOP, restraint must be shown by all!”

Violence has simmered since Palestinians launched weekly border protests on March 30 to demand the easing of a blockade on Gaza and rights to lands lost in the 1948 war of Israel’s founding. Israeli troops have killed more that 220 Palestinians during the confrontations, which have included border breaches.

A Qatari cash infusion of $15 million last week appeared to dampen Gazan anger. On Sunday, Israeli Prime Minister Benjamin Netanyahu said he hoped to reach an “arrangement” to avoid another Gaza war and ease Palestinian economic hardship.

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But hours later, a botched incursion by undercover Israeli troops in Gaza led to fighting that killed a Hamas commander, six other Palestinian militants and an Israeli colonel.

“In response to yesterday’s crime, the joint command of Palestinian factions announce the beginning of bombardment of the enemy’s settlements with scores of rockets,” Hamas said in a statement on Monday.

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In an apparent attempt to defuse tensions, Israel’s military spokesman said the special forces had not been dispatched to assassinate Hamas commanders, a tactic that led to wider conflict in the past and which has largely been abandoned.

Israeli media reports suggested the raid was mounted to gather intelligence.

Hamas, which is branded a terrorist group in the West, and Israel have fought three wars in the last decade and neither side appeared keen to precipitate another full-on conflict.

On Monday, Palestinian factions placed the onus on Israel to cease fire, saying they were prepared to increase the range of rocket fire for as long as the air barrage on Gaza persisted.

But the Israelis, jarred by dozens of civilian casualties in their border communities, appeared set on deterring Hamas.

Brigadier-General Ronen Manelis, Israel’s military spokesman, said Hamas was “leading Gaza to ruin” and that Israeli attacks on it would “intensify to the degree required”.