(Raises death toll from rain in Sichuan)

BEIJING, Sept 25 (Reuters) - Torrential rain isolated more than 20,000 people in an area of southwest China still recovering from a devastating earthquake in May, state media said on Thursday, with 14 people killed and dozens missing.

Heavy rain caused flash floods, cave-ins and landslides in mountainous Sichuan province near the epicentre of the quake, where survivors are still living in tents and pre-fabricated houses.

At least 80,000 people were killed in the May 12 earthquake.

Thirty-eight people are missing and roads and telephone lines have been cut in the storms, Xinhua news agency said.

The downpours began to pound Mianyang city and surrounding countryside in Sichuan province on Monday night, it said.

Mianyang encompasses Beichuan and other areas that were the hardest-hit counties in the Sichuan earthquake.

The rainstorms were separate to a typhoon which ploughed into south China on Wednesday, killing at least 13 people, closing schools, cancelling flights, uprooting trees and bringing down billboards in several cities. Many rivers burst their banks.

Among the dead was the chief engineer of a British freighter tossed around in the storm off Guangdong, Xinhua said.

Thousands of homes and large areas of forest and farms were destroyed, the China Daily said.

Typhoon Hagupit had since weakened as it moved into Vietnam. Hanoi said the country was on high alert for flash floods and landslides.

The army has sent a typhoon alert to more than 38,000 fishermen, while the national carrier, Vietnam Airlines, cancelled a domestic northbound flight late on Wednesday.

Hagupit, which means "lashing" in Filipino, killed at least eight people in the Philippines earlier in the week.

An earthquake measuring 5.7 struck western Nepal on Thursday, the United States Geological Survey said. Xinhua said it also hit Zhongba county in southwest Tibet. There were no immediate reports of casualties or damage. (Reporting by Nick Macfie in Beijing and Ho Binh Minh in Hanoi; Editing by Paul Tait and Ralph Boulton)

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