Samsung Electronics is seeking to block sales of the iPhone 4S only hours after it was launched, in a sign that it is shifting from defence to attack in its rapidly worsening patent dispute with Apple.

The South Korean company on Wednesday said it planned to seek injunctions against the iPhone 4S in France and Italy by filing suits in Paris and Milan, accusing Apple of infringing its patents for wireless technology in 3G mobile handsets.

“Apple has continued to flagrantly violate our intellectual property rights and free ride on our technology, and we will steadfastly protect our intellectual property. Samsung plans to file preliminary injunctions in other countries after further review,” it said.

The keenly awaited latest version of Apple’s flagship smartphone initially disappointed investors on Tuesday, as new chief executive Tim Cook’s debut product launch failed to meet expectations.

Investors who had been looking for more dramatic improvements on the iPhone 4 sent Apple stock down more than 3 per cent on Tuesday, although the shares later recovered most of that ground amid a broader market rally.

Conflict between the two companies erupted in April when Apple sued Samsung for allegedly “slavishly” copying the iPhone and iPad with its Galaxy products. Samsung, the world’s biggest technology company by sales, denies the charge and is countersuing, claiming Apple has infringed its patents.

Apple declined to comment on Wednesday. But people familiar with the company’s legal strategy said the fact that Samsung claimed the phone patents at issue in the threatened European action were “essential” could show it has a weak hand.

Essential wireless patents generally refer to those that are part of an industry standard-setting process, said Florian Mueller, legal analyst. Once established as a critical part of industry development, such patents must be licensed to all comers in a fair, reasonable and non-discriminatory fashion under competition laws. Samsung and Apple could therefore differ over how much Apple should have to pay, but a failure to resolve that would not entitle Samsung to block the product from shipping, Mr Mueller said.

The dispute cuts to the heart of the complex relationship between Apple and Samsung. Although the two compete on handsets, Samsung is also a core supplier of chips to Apple.

The litigation challenges Samsung’s cherished business strategy of being a “fast-follower”, able to catch up quickly with other companies’ products.

Samsung officials have been surprised by the ability of Apple’s lawyers to draw blood in rich western markets. A court in the Netherlands has banned three Samsung smartphones and a court in Germany last month upheld a ban on its latest tablet.

A protracted legal dispute in Australia is delaying the release of the Galaxy Tab 10.1 there. Analysts argue that even short delays can prove costly in the technology business, where products have very short life cycles. All eyes are now on the US where Apple is due to seek an injunction this month.

In recent weeks, Samsung has taken a far more belligerent stance on the cases. As well as the latest move on the iPhone 4s, the South Korean company has sought injunctions against earlier versions of the iPhone and iPad in France and the Netherlands.

Steve Jobs, former chief executive of Apple, has slammed Samsung as a copycat business but analysts say it is unclear whether his company can risk open enmity with its supplier.

Although Apple may be able to buy more chips from Taiwan, it is unlikely that smaller Taiwanese suppliers can match the more economic and broader packages of semiconductors offered by Samsung, the world’s biggest maker of memory chips.