Two Russian and two Kazakh nationals detained in Iran earlier this month have been freed.
Earlier reports said five men -- two Russian and three Kazakh citizens -- working for the Kazakh-Iranian gold exploration company Zarkuh had been arrested in Tehran on April 5.
The Russian Foreign Ministry said no concrete charges were brought against the detainees and the reasons for their arrest have not been explained.
The four men released are now in a hotel in Tehran.
The Russian Foreign Ministry said the two Russian nationals are in poor health.
The Kazakh Foreign Ministry said the Kazakh citizens are in "satisfactory" physical condition.
It said the Kazakh Embassy in Tehran is doing all it can to secure the release of the third Kazakh national.
Based on reporting by AFP and Interfax