SEOUL, Oct 17 (Reuters) - Samsung Electronics Co Ltd said on Monday that it had filed for sales bans on Apple Inc's iPhone 4S in Australia and Japan, escalating a legal battle with its archrival and biggest client.

The move came after Samsung filed preliminary injunction motions against the latest iPhone in France and Italy less than a day after the device was unveiled, claiming the product infringed its patents.

Since April, Apple and Samsung have been locked in an acrimonious legal battle in 10 countries involving smartphones and tablet computers as they jostle for the top spot in the fast-growing markets. Apple is also Samsung's biggest customer, buying mainly chips and displays.

Samsung's latest salvo came after the South Korean electronics giant suffered a series of setbacks in its ongoing legal battles with Apple.

Apple has scored preliminary injunctions against some Samsung products in Australia, Germany and the Netherlands, and further seeks to block sales of Samsung models in the United States, the key smartphone battleground.

On Thursday, a federal judge in California said during a court hearing that Samsung Electronic's Galaxy tablets infringe Apple's iPad patents, but added that Apple has a problem establishing the validity of its patents. The judge did not rule on Apple's request to bar some Galaxy products from being sold in the United States.

Samsung saw its request for a sales ban against some Apple products rejected by a Dutch court on Friday.

Samsung said on Monday that it had appealed the Australian court's decision to grant a preliminary injunction on the Galaxy Tab 10.1.

"We do respect Apple as our biggest client but we won't stand idly by, letting them infringe on our interest," Samsung Electronics CEO Choi Gee-sung was quoted as saying by a spokesperson last week.

The president and chief operating officer of Samsung Electronics, Lee Jae-yong, left for the United States on Sunday to attend Apple's private memorial service for Steve Jobs, a spokeswoman for Samsung Group said.

Local media speculated that Lee may have a separate meeting with Apple CEO Tim Cook and discuss ways to resolve the intensifying legal row, but the spokeswoman denied the reports

The California case in U.S. District Court, Northern District of California is Apple Inc v. Samsung Electronics Co Ltd et al, 11-1846.

For Apple: Morrison & Foerster; Wilmer Cutler Pickering Hale and Dorr; Taylor & Company Law Offices; Bridges & Mavrakakis.

For Samsung: Quinn Emanuel Urquhart & Sullivan.

(Reporting by Hyunjoo Jin; additional reporting by Greg Roumeliotis, Gilbert Krejger and Georgina Prodhan)

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