(CNN) -- The United Nations' special coordinator for Middle East peace expressed his concerns Thursday over reports of Hamas breaking into charity offices in Gaza and closing them down, a statement said.

"This targeting of NGOs, including UN partner organizations, is unacceptable, violating accepted norms of a free society and harming the Palestinian people," said Robert Serry, U.N. special coordinator for the Middle East Peace Process.

"The de facto authorities must cease such repressive steps and allow the re-opening of these civil society institutions without delay."

Some 80 percent of Gaza residents receive aid from NGOs -- nongovernmental organizations -- because tight import restrictions put in place by Israel since Hamas took full control of the Palestinian territory in 2007.

Israel considers Hamas a terrorist organization. Hamas does not recognize Israel's right to exist.