China's oil refinery output will increase to about 42 million metric tons in December, up 7.3 percent year-on-year, indicating that the country's economy is gradually warming up at the end of the year, said Shanghai-based industrial information provider ICIS C1 Energy.

Sinopec Group and PetroChina Co -- the two biggest oil and gas companies in the country -- will process 32.51 million tons of crude oil in total this month, up 1.27 percent compared with last month, C1 Energy said.

C1 Energy's estimates are based on data from 35 refiners owned by Sinopec and 31 refiners owned by PetroChina. Their total refining capacities take up about 67 percent of the country's total capacity.

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