Iran on Wednesday accused Israel of assassinating its nuclear scientists as part of a "war game" while it denied any role in attacks on Israeli diplomatic targets in several countries.

A letter sent by Iran's UN ambassador, Mohammad Khazaee, to the UN Security Council said Israel has been allowed to commit crimes against others with "impunity".

Israel has blamed Iran for a car bomb last week which critically injured an Israeli diplomat in New Delhi.

Georgian officials defused a second device in Tbilisi, while a suspected Iranian bomber had his legs blown off as he hurled a grenade at Thai police.

A number of arrests of people with alleged links to Iranian intelligence have reportedly been made in Azerbaijan.

Iran has in turn accused Israel of financing and training militant groups which it says have killed a number of Iranian nuclear scientists. As tensions rise over Tehran's nuclear program, there is mounting speculation that Israel plans a a military strike on Iran's nuclear facilities.

Khazaee said Israel had made "unfounded allegations and distortions" against his country over the recent attacks and bombings.

Iran "categorically rejects the allegations concerning any involvement of its officials or organs whatsoever in alleged recent terrorist operations against Israeli targets in a number of countries, namely Thailand, India, Georgia or Azerbaijan," the envoy's letter said.

Iran has "suffered from terrorist acts including assassinations of her nuclear scientists due to the tacit and explicit support extended by the Israeli regime to terrorist groups," Khazaee added.

"These operations, as well as attributing the violent acts, are part of the general war game waged by this regime against Iran."

The envoy added that Israel had carried out "covert operations, cyber warfare, psychological war and assassination of nuclear scientists," as well as threatening military strikes on Iran.

"Regrettably, the impunity with which the (Israeli) regime has been allowed to carry out its crimes thus far, has emboldened it to continue and even increase its blatant defiance of the most basic and fundamental principles of international law and the United Nations Charter," the letter said.

Western nations accuse Iran of seeking nuclear weapons, while Iran insists its nuclear enrichment program is entirely peaceful.