Four Palestinians have been shot dead by Israeli gunboats off the Gaza coast as Tel Aviv faces more criticism over its blockade of the impoverished coastal sliver. Neither the identity of the victims nor the exact whereabouts of the attack was immediately clear. Last week, Israel launched a deadly offensive on an aid convoy heading for the besieged Gaza Strip, reportedly killing at least 20 people and wounding scores more. The attack sparked an outrage across the world and drew sharp criticism from the international community against Israel's use of violent force against the humanitarian activists on the six-ship fleet. The lethal attack also stirred the world to more seriously consider Israel's defiant refusal to lift severe movement restrictions it has imposed on the Palestinian territory for years. Among the voices raised in protest was that of UN Secretary General ban Ki-moon, who said the fatalities would not have turned up if Israel had not continued the siege on Gaza.