The Hamas militant group on Monday launched a rare rocket strike on Jerusalem after hundreds of Palestinians were hurt in clashes with Israeli police at an iconic mosque, as tensions in the holy city pushed the region closer to full-fledged war.

Israel responded with airstrikes across the Gaza Strip, where 20 people, including nine children, were killed in fighting. More than 700 Palestinians were hurt in clashes with Israeli security forces in Jerusalem and across the West Bank, including nearly 500 who were treated at hospitals.

It was a long day of anger and deadly violence that laid bare Jerusalem’s deep divisions, even as Israel tried to celebrate its capture of the city’s eastern sector and its sensitive holy sites more than half a century ago. With dozens of rockets flying into Israel throughout the night, Prime Minister Benjamin Netanyahu met with top security officials and warned that the fighting could drag on, despite calls for calm from the U.S., Europe and elsewhere.

“The terrorist organizations in Gaza have crossed a red line and attacked us with missiles in the outskirts of Jerusalem,” Netanyahu said. “Whoever attacks us will pay a heavy price,” he said, warning that the fighting could “continue for some time.”

By late Monday, the military had carried out dozens of airstrikes across Gaza, targeting what it said were Hamas military installations and operatives. It said a Hamas tunnel, rocket launchers and at least eight militants had been hit.

Gaza health officials gave no further breakdowns on the casualties. At least 13 of the 20 deaths in Gaza were attributed to the airstrikes. Seven of the deaths were members of a single family, including three children, who died in a mysterious explosion in the northern Gaza town of Beit Hanoun. It was not clear if the blast was caused by an Israeli airstrike or errant rocket.

Shortly before midnight, the Israeli army said at least 150 rockets had been fired into Israel. That included a barrage of six rockets that targeted Jerusalem, some 100 kilometers (60 miles) away. It set off air raid sirens throughout Jerusalem, and explosions could be heard in what was believed to be the first time the city had been targeted since a 2014 war.

Dozens of rockets were intercepted by Israel’s Iron Dome defense system. But one landed near a home on the outskirts of Jerusalem, causing light damage to the structure and sparking a brush fire nearby. In southern Israel, an Israeli man was lightly wounded after a missile struck a vehicle.

In a statement issued early Tuesday, Hamas leader Ismail Haniyeh said the rocket attacks would continue until Israel stops “all scenes of terrorism and aggression in Jerusalem and Al-Aqsa mosque.”

The mosque is in a hilltop compound that is the third-holiest site in Islam and the holiest in Judaism. Tensions at the site, known to Muslims as the Noble Sanctuary and to Jews as the Temple Mount, have triggered repeated bouts of violence in the past.

In Monday’s unrest, Israeli police fired tear gas, stun grenades and rubber bullets in clashes with stone-throwing Palestinians at the compound.

More than a dozen tear gas canisters and stun grenades landed in the mosque as police and protesters faced off inside the walled compound that surrounds it, said an Associated Press photographer at the scene. Smoke rose in front of the mosque and the golden-domed shrine on the site, and rocks littered the nearby plaza. Inside one area of the compound, shoes and debris lay scattered over ornate carpets.

Over 600 Palestinians were hurt in Jerusalem alone, including more than 400 who required care at hospitals and clinics, according to the Palestinian Red Crescent.

Palestinians and police reported renewed clashes late Monday. Israeli police also reported unrest in northern Israel, where Arab protesters burned tires and threw stones and fireworks at security forces. Police said 46 people were arrested.

Monday’s confrontations came after weeks of almost nightly clashes between Palestinians and Israeli police in the Old City of Jerusalem, the emotional center of their conflict, during the Muslim holy month of Ramadan. The month tends to be a time of heightened religious sensitivities.

Most recently, the tensions have been fueled by the planned eviction of dozens of Palestinians from the Sheikh Jarrah neighborhood of east Jerusalem, where Israeli settlers have waged a lengthy legal battle to take over properties.

Israel’s Supreme Court postponed a key ruling Monday in the case, citing the “circumstances.”

In Washington, State Department spokesman Ned Price condemned “in the strongest terms” the rocket fire on Israel and called on all sides to calm the situation.

“More broadly, we’re deeply concerned about the situation in Israel, the West Bank and the Gaza Strip, including violent confrontations in Jerusalem,” he said. He said the U.S. would remain “fully engaged” and praised steps by Israel to cool things down, including the court delay in the eviction case.

In an apparent attempt to avoid further confrontation, Israeli authorities changed the planned route of a march by thousands of flag-waving nationalist Jews through the Muslim Quarter of the Old City to mark Jerusalem Day.

The annual festival is meant to celebrate Israel’s capture of east Jerusalem in the 1967 Mideast war. But it is widely seen as a provocation because the route goes through the heart of Palestinian areas.

Israel also captured the West Bank and Gaza in 1967. It later annexed east Jerusalem and considers the entire city its capital. The Palestinians seek all three areas for a future state, with east Jerusalem as their capital.

Meanwhile, the United Nations, Egypt and Qatar, which frequently mediate between Israel and Hamas, were all trying to halt the fighting, a diplomatic official confirmed. He spoke on condition of anonymity because he was not authorized to discuss the issue with the media.

The tensions in Jerusalem have threatened to reverberate throughout the region and come at a crucial point in Israel’s political crisis. Netanyahu failed to form a governing coalition last week, and his opponents are now working to build an alternate government.

Netanyahu pushed back against the criticism Monday, saying Israel is determined to ensure the rights of worship for all, which “occasionally requires taking a strong stand as the officers of the Israeli police, and our security forces, are doing at the moment. We back them in this just struggle.”