Norwegian oil company Statoil ASA says its fourth-quarter profits plunged 50 percent as revenue dropped because of lower oil and gas prices.

The state-controlled company said net profit in the period was 13.0 billion kroner ($2.37 billion), down from 25.5 billion kroner a year earlier.

Revenue declined by 8 percent to 159.2 billion kronor, with higher gas volumes partly offsetting a drop in prices.

The report was clouded by a terror attack last month on a jointly operated gas field in Algeria. Five of the dozens killed were Statoil employees.

Statoil said the attack highlighted the "uncertainties related to production" from the field.