Latest: Arab League to meet on Jerusalem after night of rockets and air strikes
Palestinian militant group Hamas fired dozens of rockets towards Jerusalem and southern Israel on Monday night.
Israel carried out air strikes in Gaza throughout the evening and into the early hours of Tuesday morning.
Twenty Palestinians including nine children died in the unrest, while 95 others were wounded, the Gaza Health Ministry said.
At least seven members of one family, including three children, died in an explosion in northern Gaza.
The offensive came after weeks of confrontation between Israeli police and Palestinian protesters.
Israeli Prime Minister Benjamin Netanyahu accused Hamas of crossing a “red line” with its rocket attacks on Jerusalem and promised a tough response.
“We will not tolerate an attack on our territory, in our capital, on our citizens and soldiers. Whoever attacks us will pay a heavy price,” Mr Netanyahu said.
Mr Netanyahu warned the fighting could “continue for a while”.
The rocket fire began at 6pm, the deadline Hamas had issued for Israelis to clear their forces from Sheikh Jarrah and release detained Palestinians.
The Israeli army said at least 50 rockets were fired, mostly at southern border cities. Its Iron Dome anti-missile defence system intercepted a number of the rockets.
The Israeli army said it launched a series of retaliatory attacks against Hamas militants in Gaza.
Abu Obeida, the spokesman for Hamas’ military wing, said the attack on Jerusalem was a response to Israeli “crimes and aggression” in the city.
He threatened more attacks if Israeli forces re-enter the sacred Al Aqsa Mosque compound or carry out planned evictions of Palestinian families from the East Jerusalem neighbourhood.
The militant group Palestinian Islamic Jihad also claimed to have fired more than 30 rockets into Israel, shortly after several towns were put on "Red Alert" by the Israeli military.
In Washington, White House Press Secretary Jen Psaki said the administration, including President Joe Biden, was monitoring the violence.
“We have serious concerns about the situation, including violent confrontations that we’ve seen over the last few days,” she told reporters. The US Embassy in Israel said the rocket fire was “unacceptable”.
The Palestinian Red Cross escalated its emergency level and preparedness status on Monday evening due to the rising tension.
"Ambulance teams, advanced medical units and volunteers have increased their readiness," a statement said.
The Red Cross has treated 654 individuals in East Jerusalem since May 7, of which 338 were transferred to Jerusalem hospitals. Two paramedics were injured.
As sirens sounded ahead of the incoming rocket fire, Israel's legislative assembly, the Knesset, was evacuated, a moment captured on the parliament's TV feed.
Earlier in the day, Israeli police fired tear gas, stun grenades and rubber bullets during clashes with stone-throwing Palestinians at the Al Aqsa Mosque 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, reported Associated Press. 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.
Pro-Palestine protests across the world - in pictures
Players of Chile's Club Deportivo Palestino wear keffiyeh, to show support for the Palestinian people, before their match against Colo Colo in Santiago. EPA
Club Deportivo Palestino players walk onto the pitch while wearing keffiyeh at the Monumental David Arellano Stadium, in Santiago. EPA
Palestinians in the West Bank city of Hebron protest in solidarity with Palestinian residents of East Jerusalem. EPA
Protesters with Palestinian flags shout slogans against Israel during a demonstration in front of the Israeli consulate in Istanbul, Turkey. EPA
Protesters carry Palestinian and Lebanese flags during a protest to show solidarity with the Palestinians in Jerusalem and the West Bank in downtown Beirut, Lebanon. EPA
A protester chants slogans during a sit-in in support of Palestinians at Martyrs' Square in downtown Beirut, Lebanon. AP
Protesters shout slogans and wave a flag during a protest in solidarity with Palestinians, in Rabat, Morocco. AP
Security forces disperse a protest in solidarity with Palestinians held in front of the Parliament building in Rabat, Morocco. EPA
Moroccan people protest in solidarity with Palestinians in front of the parliament building in Rabat. EPA
Jordanians protest in solidarity with the Palestinian people near the Israeli embassy in the capital Amman. AFP
People protest near the Israeli embassy in Amman, Jordan. Reuters
Police officers restrain a protester during a demonstration in solidarity with the Palestinian people, near the Israeli embassy in Jordan's capital Amman. AFP
Jordanians demonstrate to express solidarity with the Palestinian people, near the Israeli embassy in Amman. Reuters
A man holds a sign during a protest to express solidarity with the Palestinian people near the Israeli embassy in Jordan's capital Amman. AFP
Palestinians demonstrate in the occupied West Bank city of Ramallah, in solidarity with Palestinian families facing Israeli eviction orders in the Sheikh Jarrah neighbourhood of East Jerusalem. AFP
Palestinian protesters burn tyres during an anti-Israel demonstration over rising tension in Jerusalem, near the Jewish settlement of Beit El near Ramallah, in the occupied West Bank. AFP
Palestinian protesters march during an anti-Israel demonstration over rising tension in Jerusalem, near the Jewish settlement of Beit El near Ramallah, in the occupied West Bank. AFP
Palestinians protest in the occupied West Bank city of Ramallah, in solidarity with Palestinian families facing Israeli eviction orders in the Sheikh Jarrah neighbourhood of East Jerusalem. AFP
Demonstrators wave Turkish and Palestinian flags during a protest against Israel near the Israeli Consulate in Istanbul, Turkey. Reuters
Pro-Palestinian demonstrators shout slogans during a protest against Israel near the Israeli Consulate in Istanbul, Turkey. Reuters
A protester holds a poster of Al Aqsa Mosque during a demonstration against Israel in front of the Israeli Consulate in Istanbul. AFP
Palestinians gather at Jerusalem's Al Aqsa Mosque compound, ahead of a planned march to commemorate Israel's takeover of Jerusalem in the 1967 Arab-Israeli War. AFP
A Palestinian protester stands atop Al Aqsa Mosque in Jerusalem, hours before a planned march to commemorate Israel's takeover of Jerusalem in the 1967 Arab-Israeli War. AFP
A Palestinian man helps a wounded fellow protester amid clashes with Israeli security forces at Jerusalem's Al Aqsa Mosque compound. AFP
Demonstrators carry a banner that reads: "Save the Sheikh Jarrah neighbourhood, Freedom for Palestine," at a protest in Beirut, Lebanon. Palestinian residents of Sheikh Jarrah, in East Jerusalem, face eviction. AP Photo
Demonstrators chant slogans and fly the flag of Palestine during a protest in solidarity with the Palestinian people in Kuwait City, Kuwait. AFP
Protesters hold up signs expressing their solidarity with the Palestinian people, in Kuwait City, Kuwait. AFP
Protesters in Kuwait City fly the flag of Palestine and hold up placards showing their support for the Palestinian people. AFP
The flag of Palestine is reflected in the sunglasses of a protester at Irada Square, outside the National Assembly in Kuwait City, Kuwait. EPA
Protesters wearing coronavirus masks emblazoned with the flag of Palestine gather at Irada Square, outside the National Assembly in Kuwait City, Kuwait. EPA