The vessel was seized on July 17 and the crew members aboard the ship 15 Russ and two South Koreans are being held in a hotel in the city of Wonsan, located on North Korea's east coast, where the ship has also been moored.
In an announcement on its Facebook page, the Russian Embassy identified the boat as Xiangheilin-8, owned by the Northeast Fishery Company based in Nevelsk, Russia.
In its statement, the Embassy said representatives of the North Korean Foreign Ministry have been told that the boat was seized for "violating the rules of entry and stay in (North Korea)".
South Korea's Unification Ministry, which is in charge of relations with the North, was still confirming the information, a Ministry spokesperson in Seoul told Efe news.
Russian consular officials met the crew members on Monday and said they were healthy.
The Embassy said it was in close contact with the North Korean authorities and was taking all necessary measures to resolve the situation as soon as possible.
Pyongyang and Moscow share good relations dating back to the founding of North Korea under Soviet patronage in 1948.
The leaders of both countries, Kim Jong-un and Vladimir Putin, held a summit in Russia's eastern port city of Vladivostok in April, where they vowed to strengthen bilateral ties.
( With inputs from IANS )