Israel has confirmed its policy on a number of occasions.
"There will be targeted killings and other measures," an Israeli security source told reporters after resistance movements Hamas and al-Aqsa Martyrs Brigades struck at Ashdod port earlier this month, killing 10 people. "The timing depends on intelligence. The targets will be from the top down."
The targets don't come any bigger than Shaikh Yasin, who survived an assassination attempt on 10 September.
Israel also tried to assassinate Mahmud al-Zahhar, another Hamas leader, in September. His son and a bodyguard were killed in an air attack on their home.
Today's killing will be seen by many political observers as part of an Israeli plan to crush resistance in Gaza before the Zionist state withdraws completely from the Strip in its so-called "unilateral disengagement" plan.
Military sources say Israeli Prime Minister Ariel Sharon's withdrawal plan will take at least 18 months to implement.
But Palestinians feel that the withdrawal will be accompanied by an annexation of land in the West Bank, and also an Israeli rampage to break the back of the Palestinian resistance.
About 60 people have been killed in Gaza since the beginning of March including unarmed civilians, women and children.
Deputy Israeli Defence Minister Zeev Boim says the recent invasions of Gaza are related to Sharon's disengagement plan.
"The decision to escalate ongoing operations is intended to prevent Palestinians from turning the disengagement plan, if it is carried out, into some kind of heroic victory over Israel pulling out under fire," Boim told Israel army radio last week.
But the assassination policy is not new. Nearly 400 Palestinians have been killed in assassination operations conducted by the Israeli occupation army, including bystanders and children.
An Israeli air attack killed Ismail abu Shanab, a Hamas leader, in Gaza in August.
"The decision to escalate ongoing operations is intended to prevent Palestinians from turning the disengagement plan, if it is carried out, into some kind of heroic victory over Israel pulling out under fire"
Israel's deputy defence minister
Last June Israel wounded top Hamas official, Abd al-Aziz al-Rantisi in a helicopter attack on his car.
Targeted or political assassinations have been widely condemned by the international community.
In a 1998 report, the United Nations special rapporteur on extrajudicial, summary or arbitrary executions noted: “Extrajudicial executions can never be justified under any circumstances, not even in times of war.”