Referring to the investigations carried out by intelligence agencies of several countries, The Washington Post said that the "US and Middle Eastern officials now see the attempts as part of a broader campaign by Iran-linked operatives to kill foreign diplomats in at least seven countries over a span of 13 months".
These countries, according to the daily, include the United States, Azerbaijan, India, Turkey, Thailand, Pakistan and the former Soviet republic of Georgia.
In the US, authorities foiled assassination attempt on the Saudi Ambassador in Washington, while in Azerbaijan security agencies early this year made a series of arrest to foil a bid to kill American diplomats.
In India this year there was an attempt to kill an Israeli diplomat.
Israeli and Indian officials have described substantial Iranian links to a car bombing in February that seriously wounded the wife of an Israeli diplomat in New Delhi, the daily said.
"In recent weeks, investigators working in four countries have amassed new evidence tying the disparate assassination attempts to one another and linking all of them to either Iran-backed Hezbollah militants or operatives based inside Iran, according to the US and Middle Eastern security officials," the daily said.
An official report last month summarising the evidence cited phone records, forensic tests, coordinated travel arrangements and even cellphone SIM cards purchased in Iran and used by several of the would-be assailants, said two officials who have seen the six-page document, the daily said.
However, the newspaper said that the alleged attempts seem to be halted as Iran began to shift its tone after weeks of bellicose anti-Western rhetoric and threats to shut down vital shipping lanes.
In March, Iranian officials formally accepted a proposal to resume negotiations with six world powers on proposals to curb its nuclear program. "There appears to have been a deliberate attempt to calm things down ahead of the talks," a Western diplomat briefed on the assassination plots, was quoted as saying.
"What happens if the talks fail that's anyone's guess," the official said.