The Royal Australian Navy destroyer HMAS Sydney has been linked to the deaths of two whales after berthing in San Diego.

The department said the Australian and US navies were cooperating with local marine authorities and other agencies to review the incident.

“The navy takes marine mammal safety seriously and is disheartened this incident occurred,” a Defence spokesperson said.

Naval Base San Diego has secured the whale carcasses with booms until they can be removed.

Ship's hull extends 7m below waterline 

Launched in 2018, the 146-metre-long HMAS Sydney is a Hobart Class Destroyer used for air defence, surface and undersea warfare and surveillance. 

It is crewed by about 180 sailors and is fitted with sonar and radar capabilities. 

The hull extends more than 7 metres below the waterline and the ship can reach speeds up to 28 knots (52 kilometres per hour). 

Whale strikes common off California

According to US media, a US Navy spokesperson said the animals — measuring about 20 metres and 8 metres — are fin whales, which have a year-round presence off southern California. 

Research biologist John Calambokidis told local broadcaster 10 News San Diego that up to 50 whale strikes occur every year off California, with crews usually unaware until the vessel slows down and the whales become dislodged. 

"While it is possible [the Australian Navy collision] could be separate incidents, it also possible this is a mother and calf from the size distribution," he said.

He said fin whales were particularly vulnerable because of their size and because they spent a lot of time on the surface. 

More to come.