The Aug 15 attack by dozens of settlers armed with guns and Molotov cocktails, drew unusual condemnation from Israeli leaders, including Prime Minister Benjamin Netanyahu, who promised a swift investigation.

“This was a severe terror event that included setting fire to buildings and vehicles, stone and molotov-cocktail hurling, as well as live fire, resulting in the killing of one Palestinian and the injuring of another,” a statement by the police and the domestic security agency said.

The increasing incidence of settler violence against Palestinians in the West Bank since the start of the Gaza war has drawn broad condemnation internationally, including from allies of Israel such as the US.

Palestinians and rights groups regularly accuse Israeli forces of standing by while attacks by Jewish settlers against Palestinians take place and say the violence almost never results in prosecutions.

The US and a number of European countries have imposed sanctions on violent settlers and called repeatedly on Israel to do more to curb the attacks.

The Israeli authorities said the four arrested included three adults and a minor who were suspected of several acts of terrorism against Palestinians.

The investigation was continuing, the statement said.