BEIJING, May 12 (Reuters) - An earthquake with magnitude of 7.8 which struck southwestern China on Monday shook Lanzhou refinery but the plant appears undamaged, a company source said.

The epicentre of the quake was Sichuan province, the U.S. Geological Survey said, an area where there are no major oil refining plants but several major gas fields.

Sinopec <SNP.N><0386.HK> and PetroChina <PTR.N><0857.HK>, which operate the fields, could not immediately be reached for comment. Some fixed lines to the area appeared to be down.

The quake was felt in Taiwan but there were no immediate reports of damage to any of its refineries, industries sources with both government-owned CPC Corp [CHIP.UL] and Formosa <6505.TW> told Reuters.

A source at PetroChina's Jinling refinery, in Jiangsu province, said he had not felt the tremor and had not heard any reports of damage.

At Sinopec's Maoming refinery, a source also said output was unaffected and they had not felt the tremor. (Reporting by Jim Bai, Aizhu Chen and Emma Graham-Harrison, Max Lim in Singapore; Editing by Ramthan Hussain)

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