The Iranian government on Monday was down playing the brief detention of Japanese ambassador Hiroyasu Kobayashi during a private party in April.
"It was not an arrest, just a small misunderstanding," said Iranian Foreign Ministry spokesman Bahram Ghassemi.
The ambassador did not have his diplomat's identification card with him that evening, which is why he was briefly questioned by the police, Ghassemi told the ISNA news agency.
The Japanese Embassy in Tehran said Sunday that Japanese ambassador Hiroyasu Kobayashi was briefly detained and questioned in a raid by Iranian security forces and that a protest has been lodged with the Iranian Foreign Ministry.
While the reason for the raid is unclear, the incident could amount to a violation of diplomatic immunity, which guarantees that foreign diplomats cannot be arrested or detained.
Certain privileges, such as not being susceptible to prosecution under the host country's laws, are extended for diplomats.
According to the embassy, the incident happened on the evening of April 28 when Kobayashi and his wife attended a dinner hosted by a local acquaintance.
Midway through the dinner, security authorities burst in and prevented attendees from leaving the venue or from using their mobile phones.
Alcohol was served at the party and many women were not following the Islamic dress code in the presence of men, both of which are forbidden in the country.
Japanese sources said the arrest was supposed to stay secret, but was discovered by media nearly four months after the incident.