COPENHAGEN, Nov 29 (Reuters) - Swedish mining group Boliden on Wednesday said throughput of copper ore in one of the mills at its Aitik mine would be lower than expected in the fourth quarter due to an unplanned maintenance stop and unfavourable weather conditions.

The company now expects Aitik's fourth quarter throughput of copper ore to be about 9 million tonnes, down from just over 11 million tonnes expected previously, it said in a statement.

Guidance for copper and gold content was not affected by the production disruptions, Boliden added.

Damage between the trunnion and feed end on one of two primary mills at the site had caused an unplanned maintenance stop, the company said, adding that production at the affected mill line is expected to restart in December.

Seasonal and unfavourable weather conditions in November had caused elevated nitrogen dioxide levels in the air in Aitik, leading to restrictions on large parts of the industrial area, Boliden added. (Reporting by Louise Breusch Rasmussen, editing by Terje Solsvik)