A Palestinian gunman killed seven people outside an East Jerusalem synagogue during the Jewish Sabbath on Friday, in a deadly attack targeting Israelis that risked sparking widespread violence.

Israeli police said Saturday they had arrested 42 people following the deadly shooting, including members of the Palestinian gunman's family.

"The police arrested 42 suspects for questioning, some of them from the terrorist's family," a police statement said.

The shooting came a day after a major escalation in the Israeli-Palestinian conflict, including an army raid in the occupied West Bank that killed nine people, rocket fire from Gaza and retaliatory Israeli strikes.

Israel's police chief Kobi Shabtai called the shooting in the Neve Yaakov area "one of the worst attacks we have encountered in recent years." It also fell on International Holocaust Remembrance Day.

Police said that "at around 8:15 p.m. a terrorist arrived at a synagogue in the Neve Yaakov boulevard in Jerusalem and proceeded to shoot at a number of people in the area."

"As a result of the terror attack, seven civilians were pronounced dead, and three additional civilians were injured," police said.

They said the gunman fled the scene in a car but was quickly tracked down and killed in an "exchange of fire" with police.

Police have identified the gunman as a Palestinian resident of East Jerusalem, which was annexed by Israel following the 1967 Six Day War.

The surging violence comes a month after a new government, led by veteran Prime Minister Benjamin Netanyahu, took power.

Netanyahu and his extreme-right National Security Minister Itamar Ben-Gvir visited the scene on Friday, as crowds chanted "death to Arabs."

Speaking on television after visiting the scene, Netanyahu said his security cabinet would soon announce "immediate measures" in response and urged Israelis not to "take the law into their own hands."

The United States condemned the "absolutely horrific" attack.

"Our commitment to Israel's security remains ironclad, and we are in direct touch with our Israeli partners," State Department spokesman Vedant Patel told reporters.

U.S. President Joe Biden held phone talks with Netanyahu over the attack, and pledged "all appropriate means of support" to Israel over the coming days, according to a White House statement on Friday.

Just hours earlier, Washington had urged "de-escalation" over the West Bank violence and Gaza rocket fire.

United Nations Secretary General Antonio Guterres condemned the synagogue shooting as "abhorrent," while France called it "appalling."

(With input from AFP)