By Joe Cash

BEIJING, Nov 19 (Reuters) - Authorities in north China's Heilongjiang province warned locals to be on alert for Siberian tigers, after a video of a farmer narrowly escaping an attack early on Monday went viral on social media.

State and local media reported that two men had been attacked, with a 65-year-old cattle farmer surnamed Zhao requiring surgery to save his left hand.

His son told a local radio station that two tigers were on the loose. Officials have not confirmed the number of tigers or whether they have been caught.

State media said it was the first time a Siberian tiger had been spotted in Boli county.

A one-minute video clip circulating on the Chinese social media platform Weibo of another farmer going to check on the tiger's whereabouts was trending on Tuesday evening.

The video, verified by Reuters, shows the man stepping out on to the street, spotting the tiger and hurrying back to close a large iron gate, which the enormous cat hurls itself against.

Several counties have issued notices encouraging locals to report sightings of tiger droppings or footprints, keep tabs on their livestock and organise village patrols.

"Siberian tigers are generally more active in the early morning and dusk hours," one notice said. "Compared to other big cats, they can coexist with humans and are not very aggressive."

China is home to approximately 70 wild Siberian tigers, which are a protected species.

(Reporting by Joe Cash; Additional reporting by Ella Cao, editing by Ed Osmond)

((Joe.Cash@thomsonreuters.com;))