Israeli forces have reportedly opened fire on a UN relief agency convoy in the Gaza Strip during its 3-hour military ceasefire.

UN spokesman Adnan Abu Hasna said Thursday that Israeli soldiers attacked a relief truck even though the United Nations had coordinated the delivery with Tel Aviv and the vehicle was marked with a UN flag and insignia.

"It has resulted tragically in the death of one and the injury of two others," said the head of the UN relief agency in Gaza, John Ging.

Tel Aviv declared a three-hour lull in its 13-day incursion into Gaza on Thursday to allow humanitarian aid pass into the beleaguered strip.

This comes as Israeli attacks on three UN-run schools has killed at least 43 civilians and injured over 150 others -- most of whom were seeking shelter inside the school to escape the arbitrary Israeli strikes.

The United Nations had reacted in shock to the incident and stepped up calls for an independent inquiry into the attack -- the deadliest since the Israeli offensive in Gaza began Dec. 27

"There must be a serious and independent investigation into the shocking loss of civilian life that took place near the UN school and that has characterized this conflict," said deputy Middle East director for Human Rights Watch, Joe Stork.

"The building was clearly waving a UN flag, there is no safe haven in Gaza. Look at what happened in Jabaliya yesterday," said Chris Gunness the spokesman for the UNWRA, the UN agency running the school.

Tel Aviv tried to justify the incident as an attack on a militant stronghold.

The UN, however, has dismissed the Israeli claims.

Israel waged war on the Gaza Strip on December 27 and began what it claims to be a "long-term" ground offensive on the Palestinian territory last Saturday.

Thus far, the Israeli aggression has killed at least 763 Palestinians and injured over 3,100 others -- a large number of casualties are civilians.

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