Gaza  - A driver and another worker bringing humanitarian supplies from the northern crossing point of the Gaza Strip into the territory was killed when the aid convoy came under Israeli fire, a spokesman for the United Nations said.

The UN agency for Palestinian refugees, UNRWA, said it was subsequently suspending all its activity in the enclave.

In a second incident later in the day another UN convoy with international staff, heading from Gaza City to the southern town of Rafah, also came under fire, and one more person was injured.

UN Secretary General Ban Ki-moon condemned the Israeli military for the deaths, which brought to four the number of UN local relief workers killed in the Israel-Hamas conflict, now in its 13th day.

"We have suspended all movement of our staff until we receive the necessary safety assurances for our staff," a senior UNRWA official told dpa.

The first incident in which the Palestinian workers were killed took place in the late morning, while the second occurred during Israel's three-hour humanitarian lull. In both cases, the UN had coordinated its movements with the military.

Adnan Abu Hasna, from the UN agency for Palestinian refugees, UNRWA, said the convoy came under Israeli fire near the Erez crossing, killing two contracted aid workers.

The slain workers were employed by a Palestinian lorry company that is regularly used by Israel to take goods into the enclave.

The convoy had UN flags and the drivers were wearing UNRWA vests, Abu Hasna said, noting that the agency was gathering more information on the incidents.

Abu Hasna said the suspension of activity was in protest of the attack and lack of access for aid workers in the enclave as well as a safety measure.

"The United Nations is in close touch with the Israeli authorities about full investigation of this and other incidents and about the need for urgent measures to avoid them in the future," said UN spokeswoman Michelle Montas in New York.

"The secretary general calls once again for an immediate ceasefire in order to facilitate full and unhindered humanitarian access and to allow aid workers to work in safety to reach persons in need," she said. "The inability of the UN to provide assistance in this worsening humanitarian crisis in unacceptable."

The spokesman for the military said it was looking into the incident and had no comment.

Earlier in the day, the International Red Cross had said Israel was violating international law by curtailing medics' movement and preventing them, for about four days, from reaching the wounded and the dead in certain parts of the Gaza Strip.

On Tuesday, Israeli artillery shells landed just outside a UN school in Gaza, killing over 40 people. The Israeli military said it was responding to rocket fire. (dpa)