A Finnish maritime research vessel had to change its operations in international waters in the Baltic Sea to avoid interfering with Russian naval ships and a submarine, the Finnish Center for the Environment (SYKE) reported on Wednesday.

The Swedish ship Aranda was taking samples in international waters in the economic zone of Latvia on Tuesday morning when a Russian naval ship contacted Aranda and asked her to change course to avoid a submarine.

One hour later, when Aranda was taking samples in the Swedish economic zone, the Russians contacted her again and asked her to avoid a submarine and two surface vessels operating in the area.

Towards the end of the incident, a Swedish air force plane arrived to observe the situation.

The Finnish authority described the event as having taken place "under good mutual understanding."

Last autumn, there were two incidents involving Aranda and the Russian navy. At that time, the situation had been perceived as threatening by Aranda crew and researchers. This time the situation was seen as just alarming.

Aranda is a Finnish governmental ship but it is being operated by commercial ship management company VG-Shipping.