U.N. chief Ban Ki-moon on Thursday reprimanded Iran for "outrageous" comments denying the Holocaust and Israel's right to exist, and called on the two arch-nemeses to drop threats against each other.

"I strongly reject any threat by any (U.N.) member state to destroy another, or outrageous comments to deny historical facts such as the Holocaust," Ban said in a speech before a Non-Aligned summit in Tehran.

Iran's embassy in Bulgaria accused Israel on Thursday of trying to discredit Tehran and hurt bilateral relations with Sofia, with comments that Iran was behind a recent deadly attack on Israeli tourists.

In a statement, the embassy accused Israel of "abuse... aimed at compromising the Islamic Republic of Iran and creating problems in the historic and friendly ties" between Bulgaria and Iran.

Leaders from many of the world's developing states will gather in Tehran from Thursday for a two-day summit expected to sharply attack the policies of the United States and other top developed countries.

Host nation Iran, in particular, is hailing the Non-Aligned Movement (NAM) meeting as a blow to Western efforts to isolate it over its disputed nuclear activities.

Vice President Farouq al-Shara said it would be a "mistake" to keep Iran out of international efforts to end the Syrian crisis, al-Watan newspaper reported on Tuesday.

"Some countries' refusal to engage with Iran on efforts to settle Syria's crisis on the pretext that Iran is part of the problem is a clear political mistake," it quoted Shara as saying.

Iran "will never stop" its controversial uranium enrichment, the country's envoy to the IAEA said on Tuesday, on the sidelines of a Non-Aligned Movement ministerial meeting in Tehran.

"Our enrichment activities will never stop and we are justified in carrying them out, and we will continue to do so under IAEA supervision," Ali Asghar Soltanieh told reporters.

Syria's foreign minister accused the United States of being the "major player" encouraging anti-government rebels, but vowed the regime would not deploy chemical weapons in an interview published Tuesday.

Walid Muallem suggested to Britain's Independent newspaper that the U.S. may be using Syria to curb Iran's influence in the Middle East and that it had exaggerated Tehran's nuclear capabilities in order to sell weapons to Gulf countries.

Egypt on Sunday defended its idea of forming a regional contact group on Syria which would include Iran, a staunch Damascus ally, insisting that Tehran could "be part of the solution" to the Syrian crisis.

President Mohammed Morsi proposed at this month's Organization of Islamic Cooperation summit in Mecca creating such a group made up of Egypt and Iran, as well as Saudi Arabia and Turkey, two countries supporting the rebels fighting President Bashar Assad's regime.

Syria's regime will only look at negotiating with the opposition after "purging" rebels from the country, Foreign Minister Walid Muallem said on Sunday, according to talks with a visiting Iranian official reported by Iran's IRNA news agency.

"The plan for negotiations between the Syrian government and opposition will begin after purging Syria of armed groups," Muallem was quoted as saying after meeting the chairman of the Iranian parliament's national security and foreign policy commission, Aladin Borujerdi, in Damascus.

An Iranian helicopter of the Revolutionary Guards crashed in western Iran near the Iraqi border killing four Guards on Saturday, the force's website Sepahnews reported.

It did not specify the type of aircraft, saying only that the helicopter suffered "technical failure" while on a mission in Sardasht border area, which is populated by Iran's Kurdish minority.

Iran has "sanitized" to such an extent a military base where nuclear weapons research allegedly took place that the U.N. atomic watchdog may say next week there is now little point inspecting it, Western diplomats told Agence France Presse.

The International Atomic Energy Agency has been pushing Iran to allow access to Parchin, most recently at a failed meeting in Vienna on Friday, where it suspects explosives testing consistent with nuclear bomb research occurred.