You could see this one coming from a mile away: Samsung has struck back against Apple’s patent lawsuit against it with a few of its own. The Korean mobile device maker is now taking the fight international with complaints filed in South Korea, Japan and Germany, alleging that Apple (NSDQ: AAPL) is violating 10 of the company’s patents. The suits highlight how messy the mobile industry can be when it comes to competition: while Samsung and Apple are fighting it out over consumer mobile products, Samsung also a key component supplier to Apple—a relationship that now appears under threat.

While Apple’s lawsuit, filed last week in a U.S. federal court, is largely concerned with physical design issues, Samsung is attacking against a whole different level of mobile handset making.

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The areas covered in the suits, according to Reuters” title=“Reuters”>Reuters, relate to power reduction during data transmission, 3G technology for reducing errors during data transmission, and wireless data communication technology.

The suit in Seoul cited five patent infringements; the Tokyo suit cited two; and the Mannheim suit named three.

Although it does not take the opportunity, in these suits, to defend itself against Apple’s design copy allegations, Samsung nevertheless makes it clear that it is filing these suits as a way of defending itself against Apple’s earlier patent suit:

“Samsung is responding actively to the legal action taken against us in order to protect our intellectual property and to ensure our continued innovation and growth in the mobile communications business.”

If not settled soon, these suits could threaten one of the biggest supply deals in the smartphone industry today. Last year, Apple was Samsung’s second-biggest customer, after Sony Corp. (NYSE: SNE), for some key mobile components, according to AFP. Apple contributed $5.68 billion to Samsung’s $142 billion in revenue.

And in Apple’s earnings, reported Wednesday, Tim Cook noted that Apple is currently Samsung’s biggest customer for liquid crystal display panels and semiconductors.

What is at the basis of this lawsuit—operating systems or hardware? Reuters (NYSE: TRI) notes that “operating systems have emerged as the key battlefield for dominance of the world’s smartphone market.” Ahe media certainly does love to cover an “Android versus iOS” story, and it is true that Android handsets have overtaken sales of iOS handsets in many markets. But in the cases of these suits, at least, Android, and operating systems overall, do not appear to be the crux of the issue for either company.

Samsung is certainly a major competitor, currently the biggest, with its Galaxy line of products, which range not only from handsets but to several models of tablets.

What happens next? Apple would not comment on whether it expected to take its case beyond U.S. borders, but these suits may have made that into more of a possibility. And it will be interesting to see whether Apple goes after any other Android-based handset makers over design issues—as Samsung is certainly not the only company making products with touchscreens and sleek lines that look an awful lot like Apple’s designs.

On another level, this might be a good time for Samsung’s component competitors to get in touch with Cupertino in case it needs a plan-B for all those new iPads and iPhones it’s making to meet demand.

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