new york | The battle between Israel and the United Nations agency that aids Palestinians intensified on several fronts this week.

First, Israel charged that Palestinians in Gaza used a U.N. ambulance to transport a rocket.

Then the U.N.’s top refugee official admitted that some of his staff are Hamas members.

A day later, the Israel Defense Forces chief of operations, Yisrael Ziv, said that Israel had arrested 13 Palestinians employed by the United Nations on suspicion of terrorism links.

Together, the developments provided more fodder to those who accuse UNRWA, the U.N. Relief and Works Agency, of turning a blind eye to terrorism in its midst.

And they highlighted the complicated — and contentious — relationship that exists between Israel and the U.N. agency.

Even as Israel climbed down a bit Tuesday, Oct. 5, saying it needed to further investigate whether the video image on which the latest charge was based actually depicted a rocket, critics of the United Nations asserted that the developments show the agency’s tolerance of terrorist activity within its refugee camps is tantamount to complicity.

UNRWA — which provides humanitarian assistance, education services and health care to 4.1 million Palestinians, 1.3 million of whom live in 59 UNRWA refugee camps in Gaza, the West Bank, Lebanon, Syria and Jordan — has long rejected the charge.

The agency’s defenders respond that some of Israel’s supporters are campaigning to discredit an institution that promotes the rights of Palestinian refugees.

Where Israel accuses, and sometimes arrests, UNRWA staffers for terrorist activities or abuse of U.N. facilities, the agency says that at most, such instances represent the work of a few bad apples.

To some U.N. watchers, the problem is systemic.

“There may be individuals who do things, but it happens within a context that is not unsupportive of terrorist activities,” says Harris O. Schoenberg, a longtime nongovernmental activist at the United Nations and the author of “Combating Terrorism: The Role of the U.N.” The United Nations “is basically tilted to the Arab side, and within that context, UNRWA is one of the worst examples.”

On Monday, Oct. 4, Israel’s ambassador to the United Nations, Dan Gillerman, delivered to U.N. Secretary-General Kofi Annan aerial footage purported to show a Palestinian loading a Kassam rocket into the back of a van clearly marked “U.N.”

Gillerman called for a full U.N. investigation and the firing of UNRWA’s commissioner-general, Peter Hansen.

After viewing the footage, the Gaza-based Hansen — a native of Denmark — said the long, thin item carried by a man in the video was not a weapon but a folded-up, portable stretcher.