Academics and specialists from Iran, the United States and Europe have been meeting regularly in the Swiss city of Geneva for high level but informal talks.
Switzerland's Foreign Minister Micheline Calmy-Rey said she was aware of the ongoing contacts over the past few years but had not played an active role.
"The talks are on a purely informal level and the foreign ministry is not involved," Calmy-Rey said on Tuesday.
The meetings – known as the Track II process – involving academics from Iran and the US, European Union states, Switzerland, Arab countries and Israel have all been held in Geneva, according to an article in Tuesday's Le Temps newspaper.
The Geneva-based daily says about 30 participants were present at the meetings which took place mainly in Geneva, but also in other European cities. The last talks were reportedly held from March 6-8.
In total, up to 400 people have attended secret talks but are said to want to remain anonymous for fear of reprisals by the Iranian government.
Washington and Tehran broke off diplomatic relations 30 years ago in the wake of Iran's Islamic revolution. Switzerland has been representing the interests of the US in Tehran since 1980.
Mutual understanding
Le Temps also quotes an unnamed professor who has participated in the secret talks as saying that the dialogue can help to further mutual understanding.
He says participants can speak freely and are less tempted to take political stands in the closed-door meetings.
Such meetings have taken place with the approval of Tehran and Washington, Le Temps believes.
It says a person close to the Iranian government and an ambassador from another state were present at a gathering at the beginning of March.
Nuclear
The participants, which included strategic and nuclear experts and international relations specialists, reportedly discussed Iran's nuclear technology.
Iran, under investigation by the International Atomic Energy Agency (IAEA), denies it is seeking a nuclear arsenal. It claims its uranium enrichment work is to supply energy for peaceful means.
Last week, the IAEA welcomed a coordinated approach by the US and Russia to pursue diplomacy on Iran instead of policy focused isolating and threatening the Islamic republic.
Swiss Info