Pool/NTB Scanpix/via REUTERS
The shipwrecked Norwegian frigate KNM Helge Ingstad during a salvage operation near Bergen, Norway, February 26, 2019.
Two crane ships early on Tuesday began raising a submerged Norwegian navy frigate that collided with an oil tanker in November and has been stranded off Norway's west coast since, Norway's armed forces said.
The collision with the Malta-flagged tanker Sola TS injured eight people and caused the temporary closure of a North Sea crude export terminal, Norway's top gas processing plant, and several offshore fields.
Read more: Norway has released video from inside the elite warship that sank after getting rammed by a tanker
Raising the Helge Ingstad, one of Norway's five frigates, is expected to take five to six days and will require calm weather - maximum wave height during the operation cannot exceed a half-meter, or about one and a half feet, the armed forces said.
"The work must be synchronized, so the cranes must be completely stable, next to each other," the armed forces said in a statement. The salvage operation has already been postponed several times due to rough weather.