UN Secretary General Ban Ki-moon called on Israel Wednesday to immediately lift its blockade of the Gaza Strip saying it was "wrong" and "unproductive."

"The long-running closure imposed on the Gaza Strip is counter-productive, unsustainable and wrong. It punishes innocent civilians. It must be lifted by the Israeli authorities immediately," Ban told reporters in New York.

Israel and Egypt closed their border crossings with the Gaza Strip after Hamas seized control of the enclave in June 2007. The blockade has led to a drastic deterioration in the humanitarian situation in Gaza.

Despite criticism from the international community, Israel has refused so far to lift the blockade, saying it is "an act of self-defense in the face of Hamas' continuing aggression."

On Monday, the Israeli military stormed the six-ship Freedom Flotilla, carrying some 10,000 tons of aid and up to 700 human rights activists to Gaza, in neutral waters in the Mediterranean Sea. The operation claimed the lives of at least 9 people. Arab media reports put the death toll at close to 20.

The UN chief said he would appoint an independent commission to investigate the Israeli attack and demanded that Israeli authorities cooperate with the UN probe.

"The Israeli authorities must provide, as soon as possible, a full and detailed accounting of the events surrounding the incident, including information on the detained, wounded and killed," he said.

UNITED NATIONS, June 3 (RIA Novosti)