Updated

TEHRAN, Iran -- Iran plans to complain Friday to the United Nations about alleged U.S. "terror" operations, including assassination of its nuclear scientists, said its top nuclear negotiator, Saeed Jalili, at an anti-U.S. rally.

Jalili said the Swiss ambassador to Iran will be summoned to the Foreign Ministry Friday to be handed "documents of U.S. terror plots against Iran."

Copies of the documents will be presented by Iran's U.N. envoy to the Secretary-General Ban Ki-moon in New York later Friday, he said.

"The U.S. is employing terrorism to promote its objectives ... we will sue the United States," he told an anti-U.S. rally in the capital Tehran. "The U.N. needs to take the necessary measures to prosecute and punish the U.S. government for directing terrorist activities (against Iran)."

Tens of thousands of people, most of them students bused in to the site, rallied to mark the anniversary of the seizure of the U.S. Embassy by militant students in 1979. The takeover of the embassy lasted more than a year.

They responded to Jalil's words by chanting, "Death to the U.S."

"This question still remains that why people on the U.S. sanctions list are assassinated in Iran," Jalili told the crowd, a reference to the killing of three Iranian nuclear scientists by gunmen in recent years. "What relationship exists between assassinations and U.S. sanctions other than terrorists being directed by the U.S," he said

The protesters held a poster of President Barack Obama with a captions reading, "wanted, dead or alive" and "Obama terrorist." The poster showed the photos of three Iranian assassinated nuclear scientists. Iran has charged the killings were directed, financed and supported by the U.S. and Israel.

Iran is already embroiled in a spat with the U.S. over allegations that Iranian agents were involved in a plot to kill the Saudi ambassador to the United States. Iran has dismissed the U.S. claims as "absurd", without any "legal logic."

Two men, including an alleged member of Iran's special foreign actions unit known as the Quds Force, have been charged in New York federal court with conspiring to kill the Saudi diplomat, Adel Al-Jubeir.

Tensions have increased further in recent days after several American neoconservatives, including retired U.S. Army general Jack Keane and former CIA agent Reuel Marc Gerecht, urged the Obama administration to use covert action against Iran and target some of its top officials, including Quds Force chief Qasem Soleimani. The two testified last week before a U.S. Congressional subcommittee.

In Tehran, demonstrators chanted slogans backing the Quds Force.

"We support you, the Quds Force. We support you, Soleimani," they chanted.

The U.S. is also highly critical of Iran's nuclear program. Washington has accused Iran of seeking to develop nuclear weapons. The U.S. and other nations say they are stepping up their campaign to press Iran to halt the program, after several rounds of U.N. sanctions.

Iran has denied the charges, saying its nuclear program is geared toward generating electricity and producing medical radioisotopes needed to treat cancer patients.