Shots were fired during the Israeli military鈥檚 hours-long detention of a convoy of United Nations vehicles in Gaza, the UN Secretary General鈥檚 spokesperson said Tuesday.

The situation 鈥渆scalated quickly鈥 after the Israel Defense Forces (IDF) stopped the convoy at a checkpoint on Monday and demanded to take two of its 12 passengers for questioning, according to the spokesperson, Stéphane Dujarric.

Dujarric said the Israeli soldiers had pointed their weapons at the UN personnel and that at some point during the incident 鈥渟hots were fired.鈥

He said IDF tanks and bulldozers then 鈥減roceeded to ram the UN vehicles from the back and front, compacting the convoy with UN staff still inside.鈥

鈥淥ne bulldozer dropped debris on the first vehicle, while Israeli soldiers threatened staff, making it impossible for them to safely exit their vehicles,鈥 he added.

The convoy was later released and UN officials have confirmed their staff returned safely to a UN base.

CNN has asked the IDF for comment on Dujarric鈥檚 account of the incident, which took place at the Wadi Gaza checkpoint.

Previously, the IDF said it had acted 鈥渇ollowing intelligence that a number of Palestinian suspects were present in the convoy.鈥

The Israeli military had also claimed previously that the convoy was not involved in the transport of polio vaccines but was being used instead to exchange UN personnel.

However, the UN has insisted that the convoy was involved in polio vaccinations and contained national and international staff members who were meant to be rolling out the campaign for children in Gaza City and northern Gaza.

Dujarric said that despite the incident, vaccinations were able to begin in northern Gaza on Tuesday 鈥 the third phase of the UN-led campaign which is expected to continue through Thursday.

On Monday, Philippe Lazzarini, chief of the UNWRA 鈥 the UN鈥檚 main agency for Palestinian humanitarian relief 鈥 criticized the IDF鈥檚 conduct in the incident as 鈥渢he latest in a series of violations against UN staff including shootings at convoys and arrests by the Israeli Armed Forces at checkpoints despite prior notification.鈥