Two beluga whales have been evacuated from an aquarium in war-torn Ukraine to Spain by road and plane in a "high-risk" operation, officials at their new home said Wednesday.

The whales, a 15-year-old male named Plombir and a 14-year-old female named Miranda, arrived "in delicate health" at the Oceanagrafic aquarium in Spain's Mediterranean port of Valencia on Tuesday evening officials there said.

They had completed "a gruelling journey across the war zone", the aquarium said in a statement.

They were first transported overland from the NEMO Dolphinarium in Kharkiv in northeastern Ukraine to the country's southern port of Odesa, a 12-hour drive.

After health checks, they were taken across the border to Chisinau, the capital of Moldova, from where they were flown in a six-seat chartered plane to Valencia.

"The high-risk, complex rescue operation presented numerous challenges and required multi-national collaboration," the statement said.

Experts with the Georgia Aquarium and SeaWorld in the United States took part in the rescue.

A team of medical and nutritional experts are looking after the belugas in Valencia, and two Ukrainian caregivers will stay with them for several weeks to help with their transition.

"This courageous rescue constitutes a historic milestone worldwide in terms of animal protection," said the head of the regional government of Valencia, Carlos Mazon.

Russian artillery fire against Kharkiv, Ukraine’s second largest city, had intensified in recent weeks, with bombs falling just a few hundred metres from the aquarium where the whales lived.

The director of zoological operations at Valencia's Oceanografic aquarium, Daniel Garcia-Parraga, said if the whales had stayed on in Kharkiv "their chances of survival would have been very slim".

Since Russia invaded Ukraine in 2022, the NEMO Dolphinarium in Kharkiv has evacuated several seals, sea lions and dolphins, but evacuating the belugas required months of preparations due to their size.