There is irrefutable proof of Iran's role in Saudi envoy's assassination plot: Obama

US President Barack Obama has said that there was irrefutable proof that Iran had conspired to assassinate the Saudi ambassador to Washington.

While Obama accused the Iranian government of reckless behaviour, the US State department said it had been in "direct contact" with Tehran about the alleged plot.

"Now those facts are there for all to see. We would not be bringing forward a case unless we knew exactly how to support all the allegations that are contained in the indictment," the BBC quoted Obama, as saying.

Two men were charged in a New York federal court on Tuesday with conspiring to kill the Saudi envoy.

The indictment says one of the accused approached a US informant, who was posing as a member of a Mexican drug cartel, to carry out the assassination.

While Iran has branded the claims as a fabrication of facts, Obama said there could be no disputing the facts of the case. 

"We believe that even if at the highest levels there was not detailed operational knowledge, there has to be accountability with respect to anybody in the Iranian government engaging in this kind of activity. The important thing is for Iran to answer the international community, why anybody in their government is engaging in these kinds of activities," he added.