A total of 137 people were on board the frigate while 23 were on the tanker, which was flying the Maltese flag, the official said.
A collision between the frigate Helge Ingstad and the tanker TS Sola off the Sture terminal near Bergen in western Norway has led to the closure of the Vestprosess pipeline and Kollsnes gas processing plant. The Norwegian Accident Investigation Board, the Defense Accident Investigation Board and the Maltese Marine Safety Investigation Unit are all investing the incident.
It is unclear what caused the collision but several oil and gas terminals were shut down as a precaution. The ship had recently participated in the Trident Juncture exercise, one of NATO's largest training events in recent years.
"We are working on stabilizing the vessel", Norwegian Navy Counter-Admiral Nils Andreas Stensoenes told a news conference, adding that the eight injured were all Navy crew.
Firefighters have also confirmed the frigate is listing as it takes on water.
Oil output from the fields delivering to the Sture terminal was around 350,000 barrels per day in August, the latest data available from the Norwegian Petroleum Directorate showed.
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The Navy quickly evacuated all the crew except for 10 essential staff members to prevent a possible fuel leak.
"According to our assessments, there's no reason to believe that anything, like an accident, could happen with the weapons" on board, he said.
He said the frigate had been pushed by towboats into shallow water where it could not sink fully.
"[The collision is] fairly unusual given that one is a highly modern military vessel - the pride of the Norwegian navy - which should detect and avoid a huge tanker".
Although the tanker was undamaged, the £465 million frigate took on large quantities of water and was in danger of sinking when the captain took her into shallower water before running her aground.