According to the Ministry of Foreign Affairs, there will be some restrictions for land entry into Iran from 10 Mar. 2013 until further notice.
Tourists arriving on public transportation (trains, coaches, ferries) can still enter Iran with a valid visa. However, immigration officers may want to match their point of entry with the itinerary submitted with their visa application.
Tourists traveling with their own vehicles (cars, motorcycles, bikes, on foot) need to mention this in their visa application, so that their program is confirmed before issue of the visa. Those arriving on land borders may be deported, even holding a valid visa, if they have not mentioned this in their visa application.
The above points are our best understanding based on quotes by the MFA's visa officers and IranianVisa.com is not responsible for the accuracy of these information.
Should you have any question in this regard, please contact info@iranianvisa.com.