Oil output rose slightly in November from October but was 3.9 percent below the Norwegian Petroleum Directorate's (NPD) forecast for the month, the agency said on Wednesday, while adding that gas output was 6.5 percent lower than expected.

"The main reasons that production in November was below forecast is the shutdown of the Sture oil terminal and the Kollsnes gas processing plant after a collision between a crude tanker with a military vessel and technical problems on some fields," the NPD said.

The Nov. 8 collision off Norway's west coast, in which the Helge Ingstad frigate sank, caused only light injuries to its crew.

The cause of the incident is still subject to several investigations by authorities.