Bahais, whose headquarters are in Haifa, are seen as heretics in Iran
Seven members of the Bahai faith have been put on trial in Iran.
The defendants face charges of spying for foreigners, cooperating with Israel and "corruption on Earth", a charge which carries the death sentence.
The Bahai religion is banned by the Islamic revolutionary leadership of Iran which considers it heretical.
The group have been held since their arrest in 2008. The US government has condemned the trial, expressing concern about Iran's treatment of Bahais.
"The United States strongly condemns the Iranian government's decision to commence the espionage trial against seven leaders of the Iranian Bahai community," said US State Department spokesman PJ Crowley.
"We are deeply concerned about Iran's ongoing persecution of Bahais and treatment of other members of religious minorities who continue to be targeted solely on the basis of their beliefs," Mr Crowley added.
The group are being tried in a revolutionary court in Tehran.
"All the activities of the outlawed Bahai's sect in Iran is being led by its global centre based in Israel," a statement from the trial, cited by state news agency ISNA said.
"Based on the evidence and the defendants' confessions, they held meetings with ambassadors of different Western countries and discussed information and actions with them," it added.
It is not clear how long the trial of the seven Bahais will last
The Bahai faith was founded in Iran in the 19th Century but it has long been banned in its country of origin.
The Bahais consider Bahaullah, born in 1817, to be the latest prophet sent by God. Followers of the Bahai faith have faced discrimination in Iran both before and after the 1979 Islamic revolution.
Bahai groups say some 300,000 members remain in Iran. Hundreds of followers have been jailed and executed since 1979, the Bahai International Community says.
Iran denies it has detained or executed people because of their faith.
The religion has a large temple in Haifa, northern Israel, a country which has very fraught relations with Iran.