Photographic evidence has confirmed unexpected sightings of bottlenose dolphins in the Baltic Sea off the coast of Poland.

The first sightings were reported to the Institute of Oceanography at the University of Gdańsk on 8 August.

The dolphins had apparently been spotted near Poland's popular Hel Peninsula, on the western side of the Gulf of Gdańsk.

The species had not been sighted in the area since the late 19th century.

“We received this information with customary reserve, waiting for proof that would authenticate the sightings, for example in the form of another similar report,” the institute noted on its website.

Similar reports were soon forthcoming, but from the other side of the Gulf of Gdańsk.

Two bottlenose dolphins, apparently the same as those seen previously, were later seen near Klaipeda, Lithuania.

The Lithuanian Sea Museum photographed the animals.

“Dolphins are like people and they are constantly looking for new places to explore,” Professor Krzysztof Skóra of the University of Gdańsk told the Gazeta Wyborcza daily.

However, he stressed that it is unlikely that the appearance of the bottlenose dophins heralds any kind of trend, as the Baltic is not their natural habitat. (nh/rk)