Israel on Thursday formally banned the main United Nations aid agency for Palestinian refugees from operating on its territory. Humanitarian officials warn could have a disastrous impact on aid delivery and jeopardize regional stability in the long term.

Tens of thousands of Palestinian refugees in Israeli-occupied East Jerusalem were set to lose education, healthcare and other services provided by U.N. agency UNRWA as an Israeli ban on the organisation takes effect on Thursday.

On Thursday, laws passed by Israel in October come into effect banning the UN’s Palestinian refugee agency, known as UNRWA, from Israeli territory and prohibiting Israeli officials from any contact with the agency.