A senior United Nations official who is regarded as a harsh critic of Israeli policy said Monday that he received death threats through the Internet, though no evidence has yet to emerge linking the affair to the Middle East crisis.

A spokesman for UN General Assembly President Miguel d'Escoto Brockmann says U.S. authorities have been asked to help investigate online death threats against his boss.

Enrique Yeves said Monday that the threats against d'Escoto were posted during the past week. He did not specify the nature of the threats or say where they were posted, but called them "very serious."

Yeves did not identify the bloggers or their specific threats against D'Escoto.

He revealed the threats, which he said occurred within the past week, during a series of complaints about the Israelis, but he later denied there was any connection.

D'Escoto, a Roman Catholic priest with openly leftist views, has been critical of the United States and of Israel's treatment of the Palestinians. He was quoted in an Israeli newspaper in November as saying the international community should consider a boycott, divestment and sanctions against Israel similar to those used against South Africa decades earlier.

Relations between Israel and the UN have been rocky of late due to Israel's decision to banish a human rights envoy of the organization, a move that was criticized by d'Escoto.

Israel's decision to expel a U.S. expert on human rights was a "dangerous" move that contravened mandates given to rights advocates working for the United Nations, the UN General Assembly president said Monday.

The official, Richard Falk, was detained at Jerusalem's airport on Sunday and then deported back to the United States. Falk's mandate, given by the 192-nation assembly, is to assess the situation in Palestinian territories.

Foreign Minister Tzipi Livni said on Monday that Falk was "unwelcome in Israel."

Foreign Ministry statement said Falk's visit was uncoordinated and was conducted without the state's authorization and he was therefore turned around.

Israel has long complained about the mandate Falk took over earlier this year, saying it is biased in favor of the Palestinians and prevents the expert from making any comments about human rights abuses committed against Israelis.

He had also personally infuriated Israelis when he compared Israeli actions in the Palestinian territories with those of the Nazis during World War II.