The army had previously given a toll of seven killed during the strike Thursday at Tulkarem refugee camp, but added five more names to the figure, saying the group included Hamas and Islamic Jihad members that were planning an imminent attack.

"The IDF (military) and ISA (internal security) conducted a joint operation to strike terrorist operatives who were planning to carry out a terror attack against Israeli civilians in the immediate future," the military said in a statement.

The Palestinian health ministry said at least 18 people were killed during the air strike on a building in Tulkarem.

A source within the Palestinian security services told AFP the air raid was the deadliest in the West Bank since 2000.

Germany called "shocking" the "high number of civilian casualties", and the United Nations rights office called it "part of a highly concerning pattern of unlawful use of force" in the West Bank.

Tulkarem was one of the towns and Palestinian refugee camps targeted during a large-scale Israeli military operation in late August against militants based in the West Bank.

Major Israeli operations in the West Bank are sometimes occurring "at a scale not witnessed in the last two decades," United Nations human rights chief Volker Turk said last month.

Violence in the West Bank has surged alongside the war in Gaza which began after Hamas attacked Israel on October 7.

Since that attack, Israeli troops or settlers have killed at least 701 Palestinians in the West Bank, according to the Ramallah-based health ministry.

At least 24 Israelis, including members of the security forces, have been killed in Palestinian militant attacks in the territory during the same period, Israeli officials say.

Israel has occupied the West Bank since 1967, and its forces regularly make incursions into Palestinian communities.

But the raids since August have marked an escalation.