Israeli troops have killed two senior Hamas militants in a raid on a house in the West Bank city of Hebron.
The Israeli army said the militants were wanted for involvement in connection with the killing of four Israeli settlers, which occurred when Palestinian gunmen opened fire on their car near Hebron.
Hamas' military wing, the Al-Qassam Brigades, has issued a statement vowing to avenge the deaths.
Thousands of Hamas supporters also attended a mass rally in Gaza City to protest against the killings.
The operation has raised additional tensions as peace talks remain in difficulty over the construction of Israeli settlements in the West Bank.
Israeli Prime Minister Benjamin Netanyahu has rebuffed pressure from the Palestinians, the US and the international community to extend restrictions on Israeli settlement building in occupied territories.
The Palestinians have threatened to quit the talks if there is no extension.