By Sophie Yu and Byron Kaye

BEIJING/SYDNEY (Reuters) - China has begun an anti-dumping probe into imports of Australian wine, it said on Tuesday, a move that knocked a fifth off the market value of Australia's biggest winemaker and is likely to worsen tension between the nations.

The investigation by China's commerce ministry will look at imports of wine from Australia in containers of two litres or less in 2019, the ministry said in a statement, and examine any damage to the domestic wine industry from 2015 to 2019.

The Chinese Alcoholic Drinks Association requested the inquiry, asking the regulator to look into 10 Australian wine producers, including Treasury Wine Estates, the maker of Penfolds, and Accolade wines.

Shares of Treasury, the world's biggest standalone winemaker, fell up to 20% on worries at the prospect of an import tax on Australian wine.

In a statement, the company said it would cooperate with any requests for information from the authorities and remained committed to China as a "priority market".

The investigation comes against a backdrop of increasing tension between the countries after Canberra called for an international inquiry into the origins of the novel coronavirus.

China is the top market for Australian wine exports and is also Australia's largest trading partner, with two-way trade worth A$235 billion ($170 billion) last year.

Beijing recently imposed dumping tariffs on Australian barley, suspended some beef imports and told Chinese students and tourists it was not safe to travel to Australia because of accusations of racism.

Australia's trade minister, Simon Birmingham, called the investigation "very disappointing and perplexing" and said China was also considering a request to investigate countervailing duties, an import tax imposed to prevent dumping or counter export subsidies.

He told reporters he had not spoken with his Chinese counterpart, or other senior government officials, since May, when he requested discussions in light of the barley tariff.

China will carry out the investigation in a "fair and just way, according to the law," said Zhao Lijian, a foreign ministry spokesman.

He rejected suggestions it was politically motivated. "This is a normal case of anti-dumping, please don't draw unnecessary associations," he told a news briefing.

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The China Alcoholic Drinks Association said Australian wine producers had cut prices and were taking market share from local companies, which had seen a rapid deterioration in production and operating conditions.