SHENZHEN, China (Reuters) - China's Anker, one of Amazon's ( AMZN ) largest sellers offering products from power banks to phone cases, has raised prices on a fifth of its products on the U.S. platform since Thursday, in a sign that tariffs on Chinese goods are being passed on to U.S. shoppers.

Some 127 Anker products have seen an average increase of 18% since Thursday last week, with the majority of those occurring after Monday, April 7, when U.S. President Donald Trump added an extra 50% import duty on Chinese goods, according to data from e-commerce services provider SmartScout.

U.S. import tariffs on Chinese products now stand at 145%. Beijing on Friday raised its tariff on U.S. goods to 125%, as a trade war between the world's top two economies intensifies.

Anker and Amazon ( AMZN ) did not immediately respond to requests for comment.

The move follows warnings from China's largest cross-border e-commerce association that many Chinese companies that sell products on Amazon ( AMZN ) are preparing to hike prices for the U.S. or quit the market due to the tariffs.

"It's the most concerted effort (to raise prices) I've seen across any brand," said Scott Needham, SmartScout's founder.

Anker, which has 5,000 employees and annual revenues of 22.17 billion yuan ($3 billion), has become a major seller on Amazon ( AMZN ) since being founded by a former Google software engineer in 2011.

On a call with investors on Monday, Anker said that it was able to raise prices as it had bargaining power and because its rivals were mainly Chinese and under similar tariff pressure, but did not provide specifics.

It also said it would explore non-U.S. markets like Europe and Southeast Asia.

($1 = 7.3218 Chinese yuan renminbi)