Jan 19 (Reuters) - Indian refiners" crude oil throughput dipped slightly in December due to unit shutdowns at some refineries and as a rapid spread of the Omicron variant of the coronavirus shadowed fuel demand outlook. Crude oil throughput in December dipped 3% to 5.08 million barrels per day (21.48 million tonnes) from the previous month, but was 2.2% higher on an annual basis, provisional government data showed on Wednesday. Indian refiners operated at an average rate of 101.2% in December, below November"s 104.6%, but up from 99.1% in the same month last year, data showed. Refineries can operate at more than their usual capacity through technical alterations. Top refiner Indian Oil Corp (IOC) (IOC.NS) last month operated its directly owned plants at 99.74% capacity. Reliance, owner of the world"s biggest refining complex, operated its plants at 95.46% capacity in December. In 2021, refinery throughputs recovered almost half of the 620,000 barrels per day loss in 2020, but demand for refined products recovered only by one third, the International Energy Agency (IEA) said on Wednesday. "In 2022, demand is expected to slightly surpass the pre-pandemic peak of 2019, with refinery runs also back to 2019 levels." India"s fuel consumption in December scaled a nine-month peak, data showed last week, although a fresh coronavirus wave may slow the gradual recovery of demand in the world"s third biggest oil consumer. Sales of gasoil, which account for about two-fifths of India"s overall refined fuel consumption, declined in the first fortnight of January as rising COVID-19 infections hit consumer spending and truck movement in the country. read more Natural gas output jumped more than 19% to 2.896 billion cubic metres year-on-year, while crude oil production fell nearly 2% to around 593,000 barrels per day (2.51 million tonnes), the government data showed.