The Israeli military said on Tuesday it had launched an operation in the occupied West Bank's Jenin that Prime Minister Benjamin Netanyahu said aimed to "eradicate terrorism" in the area.
The Palestinian health ministry, based in Ramallah, said the operation had killed 10 people, just days after a ceasefire between Israel and Hamas took effect in the Gaza Strip.
In a joint statement, the military and the Shin Bet security agency said that, alongside the Israeli Border Police, they had launched an operation dubbed "Iron Wall" in Jenin.
The Israeli government has accused Iran, which backs armed groups across the Middle East including Hamas in Gaza, of attempting to send weapons and money to militants in the West Bank.
The Palestinian Red Crescent said its first responders treated seven people injured by live ammunition and that Israeli forces were hindering their access to the area.
United Nations Secretary-General Antonio Guterres called for "maximum restraint" from security forces and said that he "remains deeply concerned", his deputy spokesman Farhan Haq said.
Israeli NGO B'Tselem accused the Israeli government of using the Gaza ceasefire as "an excuse and opportunity to ratchet up the oppression of West Bank Palestinians".
"This is not what a ceasefire looks like," it said.
Jenin governor Kamal Abu al-Rub told AFP the operation was "an invasion of the (refugee) camp".
"It came quickly, Apache helicopters in the sky and Israeli military vehicles everywhere," he added.
An AFP journalist said Palestinian security forces, who had been conducting an operation against armed factions in the area since early December, left some of their positions around the camp before the arrival of Israeli forces.
He reported the frequent sound of explosions and gunfire echoing from the camp.
The spokesman for the Palestinian security forces, Anwar Rajab, said in a statement that Israeli forces had "opened fire on civilians and security forces, resulting in injuries to several civilians and a number of security personnel, one of whom is in critical condition".
Jenin and its refugee camp are known bastions of Palestinian militancy and Israeli forces frequently launch raids against armed factions there.
In recent months, raids have increased in frequency and intensity in Jenin.
Military raids often feature military bulldozers that dig up roads, in what Israel says is a way of removing buried explosives, often leaving whole neighbourhoods cut off from each other.
Jenin's governor said that several bulldozers had entered the city on Tuesday.