JERUSALEM—The U.N. agency for Palestinian refugees suspended a Palestinian staffer Sunday, a spokesman for the U.N. agency said as Israel alleged the employee was elected to a leadership position with the Islamist group Hamas in the Gaza Strip.

Chris Gunness of UNRWA said Suhail al-Hindi, the chairman of the UNRWA Palestinian workers’ union in Gaza and the principal of a UNRWA elementary school, was suspended due to “substantial information” received by the agency.

The Israeli defence body COGAT said al-Hindi was elected to Hamas’ politburo in a secret vote this month, though al-Hindi denied that. The U.N. agency forbids its staff from holding political office.

Maj. Gen. Yoav Mordechai of COGAT said in a statement Sunday that he demanded the U.N. agency investigate the matter. Israel considers Hamas a terrorist organization.

“We have seen the latest communication from the Israeli authorities,” Gunness said. “Before that communication, and in light of our ongoing independent internal investigation, we had been presented with substantial information from a number of sources which led us to take the decision this afternoon to suspend Suhail al Hindi, pending the outcome of our investigation. As with all UN Agencies, we will ensure that a staff member’s due process rights are followed.”

The agency temporarily suspended al-Hindi in 2011 for participating in events with Hamas officials.

Israel and UNRWA have long had a rocky relationship. Israel has accused the U.N. body of co-operating with militants, while UNRWA has accused Israel of hindering its operations in the Gaza Strip.

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